Add maths/is_prime.py

Author: a18-n03

maths/is_prime.py

@@ -0,0 +1,33 @@
+"""Prime number checker."""
+
+
+def is_prime(n: int) -> bool:
+    """
+    Check if a number is prime.
+
+    >>> is_prime(2)
+    True
+    >>> is_prime(17)
+    True
+    >>> is_prime(4)
+    False
+    >>> is_prime(1)
+    False
+    """
+    if n < 2:
+        return False
+    if n < 4:
+        return True
+    if n % 2 == 0 or n % 3 == 0:
+        return False
+    i = 5
+    while i * i <= n:
+        if n % i == 0 or n % (i + 2) == 0:
+            return False
+        i += 6
+    return True
+
+
+if __name__ == "__main__":
+    import doctest
+    doctest.testmod()