diff --git a/Makefile.conf b/Makefile.conf
index 161ee9767..8ebba3ad2 100644
--- a/Makefile.conf
+++ b/Makefile.conf
@@ -11,6 +11,7 @@ SOURCES = \
 	context.cpp \
 	constants.cpp \
 	fn_utils.cpp \
+	fn_numbers.cpp \
 	functions.cpp \
 	color_maps.cpp \
 	environment.cpp \
diff --git a/src/fn_numbers.cpp b/src/fn_numbers.cpp
new file mode 100644
index 000000000..249d69856
--- /dev/null
+++ b/src/fn_numbers.cpp
@@ -0,0 +1,217 @@
+#include <cstdint>
+#include <cstdlib>
+#include <cmath>
+#include <cctype>
+#include <random>
+#include <sstream>
+#include <iomanip>
+#include <algorithm>
+
+#include "ast.hpp"
+#include "sass.hpp"
+#include "units.hpp"
+#include "fn_utils.hpp"
+#include "fn_numbers.hpp"
+
+#ifdef __MINGW32__
+#include "windows.h"
+#include "wincrypt.h"
+#endif
+
+namespace Sass {
+
+  namespace Functions {
+
+    #ifdef __MINGW32__
+      uint64_t GetSeed()
+      {
+        HCRYPTPROV hp = 0;
+        BYTE rb[8];
+        CryptAcquireContext(&hp, 0, 0, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
+        CryptGenRandom(hp, sizeof(rb), rb);
+        CryptReleaseContext(hp, 0);
+
+        uint64_t seed;
+        memcpy(&seed, &rb[0], sizeof(seed));
+
+        return seed;
+      }
+    #else
+      uint64_t GetSeed()
+      {
+        std::random_device rd;
+        return rd();
+      }
+    #endif
+
+    // note: the performance of many implementations of
+    // random_device degrades sharply once the entropy pool
+    // is exhausted. For practical use, random_device is
+    // generally only used to seed a PRNG such as mt19937.
+    static std::mt19937 rand(static_cast<unsigned int>(GetSeed()));
+
+    ///////////////////
+    // NUMBER FUNCTIONS
+    ///////////////////
+
+    Signature percentage_sig = "percentage($number)";
+    BUILT_IN(percentage)
+    {
+      Number_Obj n = ARGN("$number");
+      if (!n->is_unitless()) error("argument $number of `" + std::string(sig) + "` must be unitless", pstate, traces);
+      return SASS_MEMORY_NEW(Number, pstate, n->value() * 100, "%");
+    }
+
+    Signature round_sig = "round($number)";
+    BUILT_IN(round)
+    {
+      Number_Obj r = ARGN("$number");
+      r->value(Sass::round(r->value(), ctx.c_options.precision));
+      r->pstate(pstate);
+      return r.detach();
+    }
+
+    Signature ceil_sig = "ceil($number)";
+    BUILT_IN(ceil)
+    {
+      Number_Obj r = ARGN("$number");
+      r->value(std::ceil(r->value()));
+      r->pstate(pstate);
+      return r.detach();
+    }
+
+    Signature floor_sig = "floor($number)";
+    BUILT_IN(floor)
+    {
+      Number_Obj r = ARGN("$number");
+      r->value(std::floor(r->value()));
+      r->pstate(pstate);
+      return r.detach();
+    }
+
+    Signature abs_sig = "abs($number)";
+    BUILT_IN(abs)
+    {
+      Number_Obj r = ARGN("$number");
+      r->value(std::abs(r->value()));
+      r->pstate(pstate);
+      return r.detach();
+    }
+
+    Signature min_sig = "min($numbers...)";
+    BUILT_IN(min)
+    {
+      List_Ptr arglist = ARG("$numbers", List);
+      Number_Obj least = NULL;
+      for (size_t i = 0, L = arglist->length(); i < L; ++i) {
+        Expression_Obj val = arglist->value_at_index(i);
+        Number_Obj xi = Cast<Number>(val);
+        if (!xi) {
+          error("\"" + val->to_string(ctx.c_options) + "\" is not a number for `min'", pstate, traces);
+        }
+        if (least) {
+          if (*xi < *least) least = xi;
+        } else least = xi;
+      }
+      return least.detach();
+    }
+
+    Signature max_sig = "max($numbers...)";
+    BUILT_IN(max)
+    {
+      List_Ptr arglist = ARG("$numbers", List);
+      Number_Obj greatest = NULL;
+      for (size_t i = 0, L = arglist->length(); i < L; ++i) {
+        Expression_Obj val = arglist->value_at_index(i);
+        Number_Obj xi = Cast<Number>(val);
+        if (!xi) {
+          error("\"" + val->to_string(ctx.c_options) + "\" is not a number for `max'", pstate, traces);
+        }
+        if (greatest) {
+          if (*greatest < *xi) greatest = xi;
+        } else greatest = xi;
+      }
+      return greatest.detach();
+    }
+
+    Signature random_sig = "random($limit:false)";
+    BUILT_IN(random)
+    {
+      AST_Node_Obj arg = env["$limit"];
+      Value_Ptr v = Cast<Value>(arg);
+      Number_Ptr l = Cast<Number>(arg);
+      Boolean_Ptr b = Cast<Boolean>(arg);
+      if (l) {
+        double lv = l->value();
+        if (lv < 1) {
+          std::stringstream err;
+          err << "$limit " << lv << " must be greater than or equal to 1 for `random'";
+          error(err.str(), pstate, traces);
+        }
+        bool eq_int = std::fabs(trunc(lv) - lv) < NUMBER_EPSILON;
+        if (!eq_int) {
+          std::stringstream err;
+          err << "Expected $limit to be an integer but got " << lv << " for `random'";
+          error(err.str(), pstate, traces);
+        }
+        std::uniform_real_distribution<> distributor(1, lv + 1);
+        uint_fast32_t distributed = static_cast<uint_fast32_t>(distributor(rand));
+        return SASS_MEMORY_NEW(Number, pstate, (double)distributed);
+      }
+      else if (b) {
+        std::uniform_real_distribution<> distributor(0, 1);
+        double distributed = static_cast<double>(distributor(rand));
+        return SASS_MEMORY_NEW(Number, pstate, distributed);
+      } else if (v) {
+        traces.push_back(Backtrace(pstate));
+        throw Exception::InvalidArgumentType(pstate, traces, "random", "$limit", "number", v);
+      } else {
+        traces.push_back(Backtrace(pstate));
+        throw Exception::InvalidArgumentType(pstate, traces, "random", "$limit", "number");
+      }
+    }
+
+    Signature unique_id_sig = "unique-id()";
+    BUILT_IN(unique_id)
+    {
+      std::stringstream ss;
+      std::uniform_real_distribution<> distributor(0, 4294967296); // 16^8
+      uint_fast32_t distributed = static_cast<uint_fast32_t>(distributor(rand));
+      ss << "u" << std::setfill('0') << std::setw(8) << std::hex << distributed;
+      return SASS_MEMORY_NEW(String_Quoted, pstate, ss.str());
+    }
+
+    Signature unit_sig = "unit($number)";
+    BUILT_IN(unit)
+    {
+      Number_Obj arg = ARGN("$number");
+      std::string str(quote(arg->unit(), '"'));
+      return SASS_MEMORY_NEW(String_Quoted, pstate, str);
+    }
+
+    Signature unitless_sig = "unitless($number)";
+    BUILT_IN(unitless)
+    {
+      Number_Obj arg = ARGN("$number");
+      bool unitless = arg->is_unitless();
+      return SASS_MEMORY_NEW(Boolean, pstate, unitless);
+    }
+
+    Signature comparable_sig = "comparable($number-1, $number-2)";
+    BUILT_IN(comparable)
+    {
+      Number_Obj n1 = ARGN("$number-1");
+      Number_Obj n2 = ARGN("$number-2");
+      if (n1->is_unitless() || n2->is_unitless()) {
+        return SASS_MEMORY_NEW(Boolean, pstate, true);
+      }
+      // normalize into main units
+      n1->normalize(); n2->normalize();
+      Units &lhs_unit = *n1, &rhs_unit = *n2;
+      bool is_comparable = (lhs_unit == rhs_unit);
+      return SASS_MEMORY_NEW(Boolean, pstate, is_comparable);
+    }
+
+  }
+
+}
\ No newline at end of file
diff --git a/src/fn_numbers.hpp b/src/fn_numbers.hpp
new file mode 100644
index 000000000..dba96be0b
--- /dev/null
+++ b/src/fn_numbers.hpp
@@ -0,0 +1,45 @@
+#ifndef SASS_FN_NUMBERS_H
+#define SASS_FN_NUMBERS_H
+
+#include "fn_utils.hpp"
+
+namespace Sass {
+
+  namespace Functions {
+
+    // return a number object (copied since we want to have reduced units)
+    #define ARGN(argname) get_arg_n(argname, env, sig, pstate, traces) // Number copy
+
+    extern Signature percentage_sig;
+    extern Signature round_sig;
+    extern Signature ceil_sig;
+    extern Signature floor_sig;
+    extern Signature abs_sig;
+    extern Signature min_sig;
+    extern Signature max_sig;
+    extern Signature inspect_sig;
+    extern Signature random_sig;
+    extern Signature unique_id_sig;
+    extern Signature unit_sig;
+    extern Signature unitless_sig;
+    extern Signature comparable_sig;
+
+    BUILT_IN(percentage);
+    BUILT_IN(round);
+    BUILT_IN(ceil);
+    BUILT_IN(floor);
+    BUILT_IN(abs);
+    BUILT_IN(min);
+    BUILT_IN(max);
+    BUILT_IN(inspect);
+    BUILT_IN(random);
+    BUILT_IN(unique_id);
+    BUILT_IN(unit);
+    BUILT_IN(unitless);
+    BUILT_IN(comparable);
+
+  }
+
+}
+
+#endif
\ No newline at end of file
diff --git a/src/fn_utils.hpp b/src/fn_utils.hpp
index eaeac0228..c373a71fb 100644
--- a/src/fn_utils.hpp
+++ b/src/fn_utils.hpp
@@ -13,9 +13,6 @@ namespace Sass {
   #define ARG(argname, argtype) get_arg<argtype>(argname, env, sig, pstate, traces)
   #define ARGM(argname, argtype, ctx) get_arg_m(argname, env, sig, pstate, traces)
 
-  // return a number object (copied since we want to have reduced units)
-  #define ARGN(argname) get_arg_n(argname, env, sig, pstate, traces) // Number copy
-
   // special function for weird hsla percent (10px == 10% == 10 != 0.1)
   #define ARGVAL(argname) get_arg_val(argname, env, sig, pstate, traces) // double
 
diff --git a/src/functions.hpp b/src/functions.hpp
index fa6d5d7f0..23a789930 100644
--- a/src/functions.hpp
+++ b/src/functions.hpp
@@ -55,15 +55,6 @@ namespace Sass {
     extern Signature str_slice_sig;
     extern Signature to_upper_case_sig;
     extern Signature to_lower_case_sig;
-    extern Signature percentage_sig;
-    extern Signature round_sig;
-    extern Signature ceil_sig;
-    extern Signature floor_sig;
-    extern Signature abs_sig;
-    extern Signature min_sig;
-    extern Signature max_sig;
-    extern Signature inspect_sig;
-    extern Signature random_sig;
     extern Signature length_sig;
     extern Signature nth_sig;
     extern Signature index_sig;
@@ -72,9 +63,6 @@ namespace Sass {
     extern Signature zip_sig;
     extern Signature list_separator_sig;
     extern Signature type_of_sig;
-    extern Signature unit_sig;
-    extern Signature unitless_sig;
-    extern Signature comparable_sig;
     extern Signature variable_exists_sig;
     extern Signature global_variable_exists_sig;
     extern Signature function_exists_sig;
@@ -91,7 +79,6 @@ namespace Sass {
     extern Signature map_has_key_sig;
     extern Signature keywords_sig;
     extern Signature set_nth_sig;
-    extern Signature unique_id_sig;
     extern Signature selector_nest_sig;
     extern Signature selector_append_sig;
     extern Signature selector_extend_sig;
@@ -139,15 +126,7 @@ namespace Sass {
     BUILT_IN(str_slice);
     BUILT_IN(to_upper_case);
     BUILT_IN(to_lower_case);
-    BUILT_IN(percentage);
-    BUILT_IN(round);
-    BUILT_IN(ceil);
-    BUILT_IN(floor);
-    BUILT_IN(abs);
-    BUILT_IN(min);
-    BUILT_IN(max);
     BUILT_IN(inspect);
-    BUILT_IN(random);
     BUILT_IN(length);
     BUILT_IN(nth);
     BUILT_IN(index);
@@ -156,9 +135,6 @@ namespace Sass {
     BUILT_IN(zip);
     BUILT_IN(list_separator);
     BUILT_IN(type_of);
-    BUILT_IN(unit);
-    BUILT_IN(unitless);
-    BUILT_IN(comparable);
     BUILT_IN(variable_exists);
     BUILT_IN(global_variable_exists);
     BUILT_IN(function_exists);
@@ -175,7 +151,6 @@ namespace Sass {
     BUILT_IN(map_has_key);
     BUILT_IN(keywords);
     BUILT_IN(set_nth);
-    BUILT_IN(unique_id);
     BUILT_IN(selector_nest);
     BUILT_IN(selector_append);
     BUILT_IN(selector_extend);
diff --git a/win/libsass.targets b/win/libsass.targets
index 8bf68df60..176f29e2a 100644
--- a/win/libsass.targets
+++ b/win/libsass.targets
@@ -34,6 +34,7 @@
     <ClInclude Include="$(LIBSASS_HEADERS_DIR)\file.hpp" />
     <ClInclude Include="$(LIBSASS_HEADERS_DIR)\fn_utils.hpp" />
     <ClInclude Include="$(LIBSASS_HEADERS_DIR)\functions.hpp" />
+    <ClInclude Include="$(LIBSASS_HEADERS_DIR)\fn_numbers.hpp" />
     <ClInclude Include="$(LIBSASS_HEADERS_DIR)\inspect.hpp" />
     <ClInclude Include="$(LIBSASS_HEADERS_DIR)\json.hpp" />
     <ClInclude Include="$(LIBSASS_HEADERS_DIR)\kwd_arg_macros.hpp" />
@@ -88,6 +89,7 @@
     <ClCompile Include="$(LIBSASS_SRC_DIR)\extend.cpp" />
     <ClCompile Include="$(LIBSASS_SRC_DIR)\file.cpp" />
     <ClCompile Include="$(LIBSASS_SRC_DIR)\fn_utils.cpp" />
+    <ClCompile Include="$(LIBSASS_SRC_DIR)\fn_numbers.cpp" />
     <ClCompile Include="$(LIBSASS_SRC_DIR)\functions.cpp" />
     <ClCompile Include="$(LIBSASS_SRC_DIR)\inspect.cpp" />
     <ClCompile Include="$(LIBSASS_SRC_DIR)\json.cpp" />
diff --git a/win/libsass.vcxproj.filters b/win/libsass.vcxproj.filters
index 1f301f769..46f42ae59 100644
--- a/win/libsass.vcxproj.filters
+++ b/win/libsass.vcxproj.filters
@@ -114,6 +114,9 @@
     <ClInclude Include="$(LIBSASS_HEADERS_DIR)\functions.hpp">
       <Filter>Headers</Filter>
     </ClInclude>
+    <ClInclude Include="$(LIBSASS_HEADERS_DIR)\fn_numbers.hpp">
+      <Filter>Headers</Filter>
+    </ClInclude>
     <ClInclude Include="$(LIBSASS_HEADERS_DIR)\inspect.hpp">
       <Filter>Headers</Filter>
     </ClInclude>
@@ -275,6 +278,9 @@
     <ClCompile Include="$(LIBSASS_SRC_DIR)\fn_utils.cpp">
       <Filter>Sources</Filter>
     </ClCompile>
+    <ClCompile Include="$(LIBSASS_SRC_DIR)\fn_numbers.cpp">
+      <Filter>Sources</Filter>
+    </ClCompile>
     <ClCompile Include="$(LIBSASS_SRC_DIR)\functions.cpp">
       <Filter>Sources</Filter>
     </ClCompile>