diff --git a/maths/prime_check.py b/maths/prime_check.py
index a757c4108f24..a10cd6961318 100644
--- a/maths/prime_check.py
+++ b/maths/prime_check.py
@@ -88,3 +88,11 @@ def test_not_primes(self):
 
 if __name__ == "__main__":
     unittest.main()
+
+
+def test_large_prime(self):
+    assert is_prime(999983)
+
+
+def test_large_non_prime(self):
+    assert not is_prime(999999)