What is Armstrong number?

An n digit number is said to be an Armstrong number if the sum of n-th power of its digits is the n digit number itself. For example consider the number 371,

• The number of digits = 3
• The sum of 3rd power of digits = 3^3 + 7^3 + 1^3 =  27+343+1 = 371

Hence 371 is an Armstrong number. Some of the other Armstrong numbers are 6, 153 and 1634.

 

Checking for Armstrong Number in Java

The following program checks whether a given number is an Armstrong number.

/* Java program to check whether a given number is an Armstrong number */
public class ArmstrongChecker {

    public static void main(String[] args) {
        int number = 153;
        if(isArmstrong(number)) {
            System.out.println(number + " is an Armstrong number!");
        } else {
            System.out.println(number + " is an NOT Armstrong number!");
        }
    }
    
    public static boolean isArmstrong(int n) {
        int no_of_digits = String.valueOf(n).length();
        int sum = 0;
        int value = n;
        for(int i=1;i<=no_of_digits;i++) {
            int digit = value%10;
            value = value/10;
            sum = sum + (int)Math.pow(digit, no_of_digits);
        }
        if(sum == n) {
            return true;
        }else {
            return false;
        }
    }
    
}