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

typedef long long ll;

signed main(){
  ll N; cin >> N;
  if( N == 1 ) cout << "NO" << endl, exit( 0 );
  int ng = 0;
  for( int i = 2; 1LL * i * i <= N; ++i )
    ng |= N % i == 0;
  if( ng ) cout << "NO" << endl;
  else cout << "YES" << endl;
  return 0;
}