diff --git a/include/mruby/internal.h b/include/mruby/internal.h
index 83738506f..1d752d131 100644
--- a/include/mruby/internal.h
+++ b/include/mruby/internal.h
@@ -261,6 +261,9 @@ mrb_value mrb_bint_sqrt(mrb_state *mrb, mrb_value x);
 mrb_int mrb_bint_size(mrb_state *mrb, mrb_value bint);
 mrb_value mrb_bint_from_bytes(mrb_state *mrb, const uint8_t *bytes, mrb_int len);
 mrb_int mrb_bint_sign(mrb_state *mrb, mrb_value bint);
+mrb_value mrb_bint_gcd(mrb_state *mrb, mrb_value x, mrb_value y);
+mrb_value mrb_bint_lcm(mrb_state *mrb, mrb_value x, mrb_value y);
+mrb_value mrb_bint_abs(mrb_state *mrb, mrb_value x);
 #endif
 
 #endif  /* MRUBY_INTERNAL_H */
diff --git a/mrbgems/mruby-bigint/core/bigint.c b/mrbgems/mruby-bigint/core/bigint.c
index faf725722..5354cd7fd 100644
--- a/mrbgems/mruby-bigint/core/bigint.c
+++ b/mrbgems/mruby-bigint/core/bigint.c
@@ -1515,7 +1515,6 @@ mpz_powm_i(mrb_state *mrb, mpz_t *zz, mpz_t *x, mrb_int ex, mpz_t *n)
   mpz_clear(mrb, &b);
 }
 
-#ifdef MRB_USE_RATIONAL
 static void
 mpz_abs(mrb_state *mrb, mpz_t *x, mpz_t *y)
 {
@@ -1833,7 +1832,6 @@ mpz_gcd(mrb_state *mrb, mpz_t *gg, mpz_t *aa, mpz_t *bb)
   mpz_move(mrb, gg, &b);
   mpz_clear(mrb, &a);
 }
-#endif
 
 static size_t
 mpz_bits(const mpz_t *x)
@@ -2844,3 +2842,69 @@ mrb_bint_reduce(mrb_state *mrb, mrb_value *xp, mrb_value *yp)
   *yp = mrb_obj_value(b2);
 }
 #endif
+
+mrb_value
+mrb_bint_gcd(mrb_state *mrb, mrb_value x, mrb_value y)
+{
+  mpz_t r, a, b;
+
+  mpz_init(mrb, &r);
+  bint_as_mpz(RBIGINT(x), &a);
+  bint_as_mpz(RBIGINT(y), &b);
+
+  mpz_gcd(mrb, &r, &a, &b);
+
+  struct RBigint *result = bint_new(mrb, &r);
+  mpz_clear(mrb, &r);
+  return bint_norm(mrb, result);
+}
+
+mrb_value
+mrb_bint_lcm(mrb_state *mrb, mrb_value x, mrb_value y)
+{
+  mpz_t gcd_val, x_mpz, y_mpz, abs_x, abs_y, product, result_mpz;
+  mrb_value zero = mrb_bint_new_int(mrb, 0);
+
+  if (mrb_bint_cmp(mrb, x, zero) == 0 || mrb_bint_cmp(mrb, y, zero) == 0) {
+    return zero;
+  }
+
+  mpz_init(mrb, &gcd_val);
+  mpz_init(mrb, &abs_x);
+  mpz_init(mrb, &abs_y);
+  mpz_init(mrb, &product);
+  mpz_init(mrb, &result_mpz);
+
+  bint_as_mpz(RBIGINT(x), &x_mpz);
+  bint_as_mpz(RBIGINT(y), &y_mpz);
+
+  mpz_abs(mrb, &abs_x, &x_mpz);
+  mpz_abs(mrb, &abs_y, &y_mpz);
+
+  mpz_gcd(mrb, &gcd_val, &abs_x, &abs_y);
+  mpz_mul(mrb, &product, &abs_x, &abs_y);
+  mpz_mdiv(mrb, &result_mpz, &product, &gcd_val);
+
+  mpz_clear(mrb, &gcd_val);
+  mpz_clear(mrb, &abs_x);
+  mpz_clear(mrb, &abs_y);
+  mpz_clear(mrb, &product);
+
+  struct RBigint *result = bint_new(mrb, &result_mpz);
+  mpz_clear(mrb, &result_mpz);
+  return mrb_obj_value(result);
+}
+
+mrb_value
+mrb_bint_abs(mrb_state *mrb, mrb_value x)
+{
+  mpz_t a, result_mpz;
+
+  mpz_init(mrb, &result_mpz);
+  bint_as_mpz(RBIGINT(x), &a);
+  mpz_abs(mrb, &result_mpz, &a);
+
+  struct RBigint *result = bint_new(mrb, &result_mpz);
+  mpz_clear(mrb, &result_mpz);
+  return mrb_obj_value(result);
+}
diff --git a/mrbgems/mruby-numeric-ext/src/numeric_ext.c b/mrbgems/mruby-numeric-ext/src/numeric_ext.c
index 445464438..5acc29ded 100644
--- a/mrbgems/mruby-numeric-ext/src/numeric_ext.c
+++ b/mrbgems/mruby-numeric-ext/src/numeric_ext.c
@@ -46,6 +46,90 @@ int_remainder(mrb_state *mrb, mrb_value x)
 
 mrb_value mrb_int_pow(mrb_state *mrb, mrb_value x, mrb_value y);
 
+static mrb_int
+mrb_int_gcd(mrb_int x, mrb_int y)
+{
+  if (x < 0) x = -x;
+  if (y < 0) y = -y;
+
+  while (y != 0) {
+    mrb_int temp = y;
+    y = x % y;
+    x = temp;
+  }
+
+  return x;
+}
+
+/*
+ * call-seq:
+ *     int.gcd(other_int)  ->  integer
+ *
+ * Returns the greatest common divisor of the two integers.
+ * The result is always positive.
+ */
+static mrb_value
+int_gcd(mrb_state *mrb, mrb_value x)
+{
+  mrb_value y = mrb_get_arg1(mrb);
+
+#ifdef MRB_USE_BIGINT
+  if (mrb_bigint_p(x) || mrb_bigint_p(y)) {
+    if (!mrb_integer_p(y) && !mrb_bigint_p(y)) {
+      mrb_raisef(mrb, E_TYPE_ERROR, "can't convert %Y into Integer", y);
+    }
+    if (!mrb_bigint_p(x)) x = mrb_bint_new_int(mrb, mrb_integer(x));
+    if (!mrb_bigint_p(y)) y = mrb_bint_new_int(mrb, mrb_integer(y));
+    return mrb_bint_gcd(mrb, x, y);
+  }
+#endif
+
+  if (!mrb_integer_p(y)) {
+    mrb_raisef(mrb, E_TYPE_ERROR, "can't convert %Y into Integer", y);
+  }
+  return mrb_int_value(mrb, mrb_int_gcd(mrb_integer(x), mrb_integer(y)));
+}
+
+/*
+ * call-seq:
+ *     int.lcm(other_int)  ->  integer
+ *
+ * Returns the least common multiple of the two integers.
+ * The result is always positive.
+ */
+static mrb_value
+int_lcm(mrb_state *mrb, mrb_value x)
+{
+  mrb_value y = mrb_get_arg1(mrb);
+  mrb_int a, b, gcd_val;
+
+#ifdef MRB_USE_BIGINT
+  if (mrb_bigint_p(x) || mrb_bigint_p(y)) {
+    if (!mrb_integer_p(y) && !mrb_bigint_p(y)) {
+      mrb_raisef(mrb, E_TYPE_ERROR, "can't convert %Y into Integer", y);
+    }
+    if (!mrb_bigint_p(x)) x = mrb_bint_new_int(mrb, mrb_integer(x));
+    if (!mrb_bigint_p(y)) y = mrb_bint_new_int(mrb, mrb_integer(y));
+    return mrb_bint_lcm(mrb, x, y);
+  }
+#endif
+
+  if (!mrb_integer_p(y)) {
+    mrb_raisef(mrb, E_TYPE_ERROR, "can't convert %Y into Integer", y);
+  }
+
+  a = mrb_integer(x);
+  b = mrb_integer(y);
+
+  if (a == 0 || b == 0) return mrb_int_value(mrb, 0);
+
+  gcd_val = mrb_int_gcd(a, b);
+  if (a < 0) a = -a;
+  if (b < 0) b = -b;
+
+  return mrb_int_value(mrb, (a / gcd_val) * b);
+}
+
 /*
  * call-seq:
  *    integer.pow(numeric)           ->  numeric
@@ -353,6 +437,8 @@ mrb_mruby_numeric_ext_gem_init(mrb_state* mrb)
   mrb_define_method_id(mrb, ic, MRB_SYM(size), int_size, MRB_ARGS_NONE());
   mrb_define_method_id(mrb, ic, MRB_SYM_Q(odd), int_odd, MRB_ARGS_NONE());
   mrb_define_method_id(mrb, ic, MRB_SYM_Q(even), int_even, MRB_ARGS_NONE());
+  mrb_define_method_id(mrb, ic, MRB_SYM(gcd), int_gcd, MRB_ARGS_REQ(1));
+  mrb_define_method_id(mrb, ic, MRB_SYM(lcm), int_lcm, MRB_ARGS_REQ(1));
   mrb_define_class_method_id(mrb, ic, MRB_SYM(sqrt), int_sqrt, MRB_ARGS_REQ(1));
 
 #ifndef MRB_NO_FLOAT
diff --git a/mrbgems/mruby-numeric-ext/test/numeric.rb b/mrbgems/mruby-numeric-ext/test/numeric.rb
index bb4c461d6..4578afd26 100644
--- a/mrbgems/mruby-numeric-ext/test/numeric.rb
+++ b/mrbgems/mruby-numeric-ext/test/numeric.rb
@@ -26,6 +26,30 @@ assert('Integer#pow') do
   assert_equal(361, 9.pow(1024,1000))
 end
 
+assert('Integer#gcd') do
+  assert_equal(1, 2.gcd(3))
+  assert_equal(5, 10.gcd(15))
+  assert_equal(6, 24.gcd(18))
+  assert_equal(7, 7.gcd(0))
+  assert_equal(7, 0.gcd(7))
+  assert_equal(0, 0.gcd(0))
+  assert_equal(5, (-10).gcd(15))
+  assert_equal(5, 10.gcd(-15))
+  assert_equal(5, (-10).gcd(-15))
+end
+
+assert('Integer#lcm') do
+  assert_equal(6, 2.lcm(3))
+  assert_equal(30, 10.lcm(15))
+  assert_equal(72, 24.lcm(18))
+  assert_equal(0, 7.lcm(0))
+  assert_equal(0, 0.lcm(7))
+  assert_equal(0, 0.lcm(0))
+  assert_equal(30, (-10).lcm(15))
+  assert_equal(30, 10.lcm(-15))
+  assert_equal(30, (-10).lcm(-15))
+end
+
 assert('Integer#ceildiv') do
   assert_equal(0, 0.ceildiv(3))
   assert_equal(1, 1.ceildiv(3))