C# Program to Check Whether the Entered Number is an Armstrong Number or Not

For an Armstrong number, let us say a number has 3 digits, then the sum of cube of its digits is equal to the number itself.

For example, 153 is equal to −

1³ + 3³ + 5³

To check for it using C#, check the value and find its remainder. Here “val” is the number you want to check for Armstrong −

for (int i = val; i > 0; i = i / 10) {
   rem = i % 10;
   sum = sum + rem*rem*rem;
}

Now compare the addition with the actual value. If it matches, that would mean the sum of cubes are the same and it is an Armstrong number −

if (sum == val) {
   Console.Write("Armstrong Number");
}else {
   Console.Write("Not an Armstrong Number");
}

Example

Let us see a complete example to check whether a number is Armstrong or not.

Live Demo

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Demo {
   class ApplicationNew {
      static void Main(string[] args) {
         int val = 153, sum = 0;
         int rem;
         // check for armstrong
         for (int i = val; i > 0; i = i / 10) {
            rem = i % 10;
            sum = sum + rem*rem*rem;
         }
         if (sum == val) {
            Console.Write("Armstrong Number");
         } else {
            Console.Write("Not an Armstrong Number");
         }
         Console.ReadLine();
      }
   }
}

Output

Armstrong Number