diff --git a/lib/mjs/mjs_exec.c b/lib/mjs/mjs_exec.c
index 0213a871e..8fdb2d7e5 100644
--- a/lib/mjs/mjs_exec.c
+++ b/lib/mjs/mjs_exec.c
@@ -475,6 +475,22 @@ static int getprop_builtin_string(
     return 0;
 }
 
+static int getprop_builtin_number(
+    struct mjs* mjs,
+    mjs_val_t val,
+    const char* name,
+    size_t name_len,
+    mjs_val_t* res) {
+    if(strcmp(name, "toString") == 0) {
+        *res = mjs_mk_foreign_func(mjs, (mjs_func_ptr_t)mjs_number_to_string);
+        return 1;
+    }
+
+    (void)val;
+    (void)name_len;
+    return 0;
+}
+
 static int getprop_builtin_array(
     struct mjs* mjs,
     mjs_val_t val,
@@ -589,6 +605,8 @@ static int getprop_builtin(struct mjs* mjs, mjs_val_t val, mjs_val_t name, mjs_v
         } else if(s != NULL && n == 5 && strncmp(s, "apply", n) == 0) {
             *res = mjs_mk_foreign_func(mjs, (mjs_func_ptr_t)mjs_apply_);
             handled = 1;
+        } else if(mjs_is_number(val)) {
+            handled = getprop_builtin_number(mjs, val, s, n, res);
         } else if(mjs_is_array(val)) {
             handled = getprop_builtin_array(mjs, val, s, n, res);
         } else if(mjs_is_foreign(val)) {
diff --git a/lib/mjs/mjs_primitive.c b/lib/mjs/mjs_primitive.c
index b63a268e5..e73ae892d 100644
--- a/lib/mjs/mjs_primitive.c
+++ b/lib/mjs/mjs_primitive.c
@@ -6,6 +6,8 @@
 #include "mjs_core.h"
 #include "mjs_internal.h"
 #include "mjs_primitive.h"
+#include "mjs_string_public.h"
+#include "mjs_util.h"
 
 mjs_val_t mjs_mk_null(void) {
     return MJS_NULL;
@@ -158,3 +160,31 @@ MJS_PRIVATE void mjs_op_isnan(struct mjs* mjs) {
 
     mjs_return(mjs, ret);
 }
+
+MJS_PRIVATE void mjs_number_to_string(struct mjs* mjs) {
+    mjs_val_t ret = MJS_UNDEFINED;
+    mjs_val_t base_v = MJS_UNDEFINED;
+    int32_t base = 10;
+    int32_t num;
+
+    /* get number from `this` */
+    if(!mjs_check_arg(mjs, -1 /*this*/, "this", MJS_TYPE_NUMBER, NULL)) {
+        goto clean;
+    }
+    num = mjs_get_int32(mjs, mjs->vals.this_obj);
+
+    if(mjs_nargs(mjs) >= 1) {
+        /* get base from arg 0 */
+        if(!mjs_check_arg(mjs, 0, "base", MJS_TYPE_NUMBER, &base_v)) {
+            goto clean;
+        }
+        base = mjs_get_int(mjs, base_v);
+    }
+
+    char tmp_str[] = "-2147483648";
+    itoa(num, tmp_str, base);
+    ret = mjs_mk_string(mjs, tmp_str, ~0, true);
+
+clean:
+    mjs_return(mjs, ret);
+}
diff --git a/lib/mjs/mjs_primitive.h b/lib/mjs/mjs_primitive.h
index 6d6f91785..f1c3c8220 100644
--- a/lib/mjs/mjs_primitive.h
+++ b/lib/mjs/mjs_primitive.h
@@ -34,6 +34,11 @@ MJS_PRIVATE void* get_ptr(mjs_val_t v);
  */
 MJS_PRIVATE void mjs_op_isnan(struct mjs* mjs);
 
+/*
+ * Implementation for JS Number.toString()
+ */
+MJS_PRIVATE void mjs_number_to_string(struct mjs* mjs);
+
 #if defined(__cplusplus)
 }
 #endif /* __cplusplus */