Program:

#include <stdio.h>
#include<math.h>

int main(){
    int n,p=0,Number,ans=0,rem;
    printf("Enter the Number:");
    scanf("%d",&n);

    //Logic for find Number of digit & store in p.
    Number=n;
    while(Number!=0){
        Number/=10;
        p++;
    }


    Number=n;
    while(Number!=0){
        rem=Number%10;
        ans+= pow(rem,p);
        Number=Number/10;
    }

    if (ans==n){
       printf("\n\t%d is a Armstrong Number.",n);
    }
    else{
        printf("\n\t%d is NOT a Armstrong Number.",n);
    }

    return 0;
}


Expected O/P:

Enter the Number: 153
 
         153 is a Armstrong Number.