'''****** Задание ********
  *Простая задача.
'''
num = int(input())
prime = True
if num <= 1:
    prime = False
else:
    for divisor in range(2, int(num**0.5 + 1)):
        if num % divisor == 0:
            prime = False
            break
if prime is True:
    print('YES')
else:
    print('NO')