new_contents: print("Starting Prime Number Determining Program")
  
  
  def advanced_check_number(n):
      import math
      n_sqrt = math.sqrt(n)
      i = 3
      while i < n_sqrt+1:
          if n % i == 0:
              return False
          i = i + 2
      return True
  
  
  def check_number(n):
      # quickly discard numbers divisible by 2
      if n % 2 == 0:
          return False
      else:
          return advanced_check_number(n)
  
  number = int(input("Enter a number: "))
  is_prime = check_number(number)
  
  
  if is_prime is True:
      print (str(number) + " is a prime number")
  else:
      print (str(number) + " is not a prime number")
  
subject: add my prime number checker