CONTEST3_BAI1_KIEM_TRA_SO_NGUYEN_TO

from math import*

if __name__ == "__main__":
    check = 0
    n = int(input())
    if n < 2:
        print("NO")
    else:
        for i in range(2, int(sqrt(n))+1):
            if n % i == 0:
                print("NO")
                check = 1
                break
        if check ==0 :
            print("YES")