Program to Check if a Number is an Armstrong Number in C++

Armstrong Number

An Armstrong number (or narcissistic number) is a number that is equal to the sum of its own digits raised to the power of the number of digits. For example, 153 and 9474 are Armstrong numbers.

We will explore a method to check if a given number is an Armstrong number using C++ programming.

Method: Using a while Loop

We extract each digit, raise it to the power of the number of digits, and sum them up to check the Armstrong condition.

#include <iostream>
#include <cmath>
using namespace std;

bool isArmstrong(int num) {
    int originalNum = num, sum = 0, digit, n = 0, temp = num;
    
    // Count the number of digits
    while (temp != 0) {
        temp /= 10;
        n++;
    }
    
    temp = num;
    
    // Calculate the sum of digits raised to the power of n
    while (temp != 0) {
        digit = temp % 10;
        sum += pow(digit, n);
        temp /= 10;
    }
    
    return (sum == num);
}

int main() {
    int num;
    cout << "Enter a number: ";
    cin >> num;
    
    if (isArmstrong(num))
        cout << num << " is an Armstrong number";
    else
        cout << num << " is not an Armstrong number";
    
    return 0;
}
            

Output:

Enter a number: 153
153 is an Armstrong number