#include<iostream>
using namespace std;

int main(){
  int n;
  std::cin >> n;
  if(n == 1){
    std::cout << "NO" << std::endl;
    return 0;
  }
  for (int i = 2; i*i <= n; i++) {
    if(n%i == 0){
      std::cout << "NO" << std::endl;
      return 0;
    }
  }
  std::cout << "YES" << std::endl;
  return 0;
}