#include <algorithm>
#include <iostream>
#include <string.h>
#include <math.h>
 
using namespace std; 
 
int main(){
  long long n;
  cin>>n;
  if(n==1){
    cout << "NO" << endl;
    return 0;
  }
  if(n%2==0){
    cout << "NO" << endl;
    return 0;
  }
  for(int i = 3; i*i <= n; i+=2){
    if(n%i==0){
      cout << "NO" << endl;
      return 0;
    }
  }
  cout << "YES" << endl;
  return 0;
}