import java.math.BigInteger;
import java.util.Scanner;

public class yuki {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		BigInteger b = sc.nextBigInteger();
		for (BigInteger i = BigInteger.ONE.add(BigInteger.ONE); i.compareTo(b) < BigInteger.ZERO.intValue(); i = i.add(BigInteger.ONE)) {
			if (b.mod(i).equals(BigInteger.ZERO)) {
				System.out.println("NO");
				return;
			}
		}
		if (b.equals(BigInteger.ONE)) {
			System.out.println("NO");
			return;
		}
		System.out.println("YES");
	}
}