Check if a large number is divisible by 20 in C++

Here we will see how to check a number is divisible by 20 or not. In this case the number is very large number. So we put the number as string.

A number will be divisible by 20, when that is divisible by 10, and after dividing 10, the remaining number is divisible by 2. So the case is simple. If the last digit is 0, then it is divisible by 10, and when it is divisible by 10, then the second last element is divisible by 2, the number is divisible by 20.

Example

Live Demo

#include <bits/stdc++.h>
using namespace std;
bool isDiv20(string num){
   int n = num.length();
   if(num[n - 1] != '0')
      return false;
      int second_last = num[n - 2] - '0';
   if(second_last % 2 == 0)
      return true;
      return false;
}
int main() {
   string num = "54871584540";
   if(isDiv20(num)){
      cout << "Divisible";
   }else{
      cout << "Not Divisible";
   }
}