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

class Main {
	public static void main(String[] agrs) {
		Scanner scanner = new Scanner(System.in);
		BigInteger N = scanner.nextBigInteger(), i;
		scanner.close();
		for (i = BigInteger.ONE.add(BigInteger.ONE); BigInteger.ONE.intValue() == N.compareTo(i); i = BigInteger.ONE.add(i)) {
			if (BigInteger.ZERO.equals(N.mod(i))) break;
		}
		if (N.equals(i)) System.out.print("YES");
		else System.out.print("NO");
	}
}