C Program to Check Armstrong Number - Sum of Digits Cubed

Check Whether a Number is an Armstrong Number

#include <stdio.h>

int main() {
    int number, originalNumber, remainder;
    int result = 0;

    printf("Enter an integer: ");
    scanf("%d", &number);

    originalNumber = number;  // Save the original number

    // Iterate over each digit
    while (number != 0) {
        remainder = number % 10;            // Get last digit
        result += remainder * remainder * remainder; // Sum the cubes of digits
        number /= 10;                       // Remove last digit
    }

    if (result == originalNumber)
        printf("%d is an Armstrong number.\n", originalNumber);
    else
        printf("%d is not an Armstrong number.\n", originalNumber);

    return 0;
}

Enter an integer: 153
153 is an Armstrong number.
        

Practice: Check Armstrong Number

An Armstrong (or narcissistic) number is equal to the sum of the cubes of its digits. This program extracts each digit from the rightmost side, cubes it, adds it to a running total, and finally checks if the sum matches the original number. The classic three‑digit Armstrong numbers are 153, 370, 371 and 407.