n=int(input())
import math
def isPrime(n):
  if n == 2:
    return True
  if n % 2 == 0:
    return False
  m = math.floor(math.sqrt(n)) + 1
  for p in range(3, m, 2):
      if n % p == 0:
        return False
  return True
if n==1:
    print("NO")
    exit()
if isPrime(n):
    print("YES")
else:print('NO')