input: Write a python function to find the smallest prime number greater than a given number.
  assert smallest_prime_number_greater_than(10) == 11
  assert smallest_prime_number_greater_than(20) == 23
  assert smallest_prime_number_greater_than(30) == 31
  assert smallest_prime_number_greater_than(100) == 101
output: def smallest_prime_number_greater_than(n):
      def is_prime(num):
          if num <= 1:
              return False
          for i in range(2, int(num ** 0.5) + 1):
              if num % i == 0:
                  return False
          return True
  
      candidate = n + 1
      while not is_prime(candidate):
          candidate += 1
      return candidate