#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
using namespace std;

#define PI         acos(-1.0)
#define FOR(I,A,B) for(long long I = (A); I < (B); ++I)

typedef long long ll;

int main(){
    ll n;
    cin >> n;
    bool ok = true;
    FOR(i,2,(ll)sqrt(n)+1){
        if(n%i==0) ok = false;
    }
    cout << (ok ? "YES" : "NO") << endl;
    return 0;
}