#include <bits/stdc++.h>
using namespace std;

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