import math


def isp(N):
    two = len(["", ""])
    zero = len([])

    if N < two:
        return False

    i = ["", ""]
    while int(math.pow(len(i), two)) <= N:
        if N % len(i) == zero:
            return False
        i.append("")

    return True


N = int(input())


print("YES" if isp(N) else "NO")