Add Armstrong number check algorithmCreate is_armstrong.py

maths/is_armstrong.py

@@ -0,0 +1,20 @@
+def is_armstrong(n: int) -> bool:
+    """
+    Check if a number is an Armstrong number.
+
+    An Armstrong number (Narcissistic number) is a number that is equal
+    to the sum of its digits each raised to the power of the number of digits.
+
+    Example:
+    153 = 1^3 + 5^3 + 3^3
+    """
+
+    digits = list(map(int, str(n)))
+    num_digits = len(digits)
+    return n == sum(d**num_digits for d in digits)
+
+
+if __name__ == "__main__":
+    print(is_armstrong(153))  # True
+    print(is_armstrong(370))  # True
+    print(is_armstrong(10))  # False