Python Program to Check Armstrong Number

An Armstrong number (also called a narcissistic number) is a positive integer that equals the sum of its own digits raised to the power of the number of digits. For example, 153 is a 3-digit Armstrong number because 1³ + 5³ + 3³ = 1 + 125 + 27 = 153.

Understanding Armstrong Numbers

For a number with n digits, it's an Armstrong number if ?

abcd... = a^n + b^n + c^n + d^n + ...

Common examples include:

• 1-digit: 1, 2, 3, ..., 9 (all single digits)
• 3-digit: 153, 371, 407
• 4-digit: 1634, 8208, 9474

Method 1: Fixed 3-Digit Armstrong Number

This approach checks specifically for 3-digit Armstrong numbers ?

num = 153
sum_ = 0
temp = num

while temp > 0:
    digit = temp % 10
    sum_ += digit ** 3
    temp //= 10

if num == sum_:
    print(num, "is an Armstrong number")
else:
    print(num, "is not an Armstrong number")

153 is an Armstrong number

Method 2: General Armstrong Number (Any Digits)

This method works for Armstrong numbers of any length by calculating the number of digits first ?

def is_armstrong(num):
    # Convert to string to count digits
    str_num = str(num)
    num_digits = len(str_num)
    
    # Calculate sum of digits raised to power of num_digits
    sum_of_powers = sum(int(digit) ** num_digits for digit in str_num)
    
    return num == sum_of_powers

# Test with different Armstrong numbers
test_numbers = [153, 371, 1634, 221, 407]

for number in test_numbers:
    if is_armstrong(number):
        print(f"{number} is an Armstrong number")
    else:
        print(f"{number} is not an Armstrong number")

153 is an Armstrong number
371 is an Armstrong number
1634 is an Armstrong number
221 is not an Armstrong number
407 is an Armstrong number

Method 3: Using Mathematical Approach

This method extracts digits using mathematical operations without string conversion ?

def count_digits(n):
    count = 0
    while n > 0:
        count += 1
        n //= 10
    return count

def is_armstrong_math(num):
    original = num
    digits = count_digits(num)
    sum_of_powers = 0
    
    while num > 0:
        digit = num % 10
        sum_of_powers += digit ** digits
        num //= 10
    
    return original == sum_of_powers

# Test the function
number = 9474
if is_armstrong_math(number):
    print(f"{number} is an Armstrong number")
else:
    print(f"{number} is not an Armstrong number")

9474 is an Armstrong number

Comparison

Conclusion

Armstrong numbers are equal to the sum of their digits raised to the power of digit count. Use string conversion for readability or mathematical approach for pure numeric operations without string handling.