input: Write a python function to take an input and return a list of its prime factors.
  assert prime_factorize(81)==[3, 3, 3, 3]
  assert prime_factorize(56)==[2, 2, 2, 7]
  assert prime_factorize(97)==[97]
  assert prime_factorize(100)==[2, 2, 5, 5]
output: def prime_factorize(n):
      factors = []
      divisor = 2
      while n >= 2:
          if n % divisor == 0:
              factors.append(divisor)
              n //= divisor
          else:
              divisor += 1
      return factors