#include <bits/stdc++.h>

using namespace std;

long long mul(long long a, long long b, long long m){
	if(b==1)
		return a;
	if(b%2==0){
		long long t = mul(a, b/2, m);
		return (2 * t) % m;
	}
	return (mul(a, b-1, m) + a) % m;
}

long long pows(long long a, long long b, long long m){
	if(b==0)
		return 1;
	if(b%2==0){
		long long t = pows(a, b/2, m);
		return mul(t , t, m) % m;
	}
	return ( mul(pows(a, b-1, m) , a, m)) % m;
}

long long gcd(long long a, long long b){
	if(b==0)
		return a;
	return gcd(b, a%b);
}

bool Prime(long long x){
	if(x == 2)
		return true;
	srand(time(NULL));
	for(int i=0;i<100;i++){
		long long a = (rand() % (x - 2)) + 2;
		if (gcd(a, x) != 1)
			return false;
		if( pows(a, x-1, x) != 1)
			return false;
	}
	return true;
}

int main()
{
    long long n;
    cin >> n;
    if(Prime(n))
        cout << "YES" << endl;
    else
        cout << "NO" << endl;
    return 0;
}