import math

N = int(input())
is_prime = True
for i in range(2, math.ceil(math.sqrt(N))+1):
  if N%i == 0:
    is_prime = False 
    break

print('YES') if is_prime else print('NO')


# def is_prime(n):
#   if n == 1:
#     return False
#   for i in range(2,int(n**0.5)+1):
#     if n % i == 0:
#       return False
#   return True