input: from typing import List
  
  def is_prime(number: int) -> bool:
      """ Determine if a given number is prime or not.
      >>> is_prime(17)
      True
      >>> is_prime(20)
      False
      """
      is_prime = True
      for i in range(2, number):
          if number % i == 0:
              is_prime = False
              break
      return is_prime
  
output:     
      if number <= 1:
          return False
      if number == 2:
          return True
      if number % 2 == 0:
          return False
      for i in range(3, int(number**0.5) + 1, 2):
          if number % i == 0:
              return False
      return True
  