first understand what is armstrong number n = 153 1*1*1 + 5*5*5 + 3*3*3 do all digits cube and then add them together here we get the same value as 153 so 153 is a armstrong number code in java public static void main(String []args) { int n = 153; // we can use Scanner Class int rem = 0 , arm = 0 , c = n; while(n>0) { rem = n%10; arm = (rem*rem*rem) + arm; n = n/10; } if(arm==c) { System.out.println(c+" is a armstrong number"); } else { System.out.println(c+" is not a armstrong number"); } }