input: Write a python function to find prime factors of a given number.
  assert primeFactors(28) == [2, 2, 7]
  assert primeFactors(100) == [2, 2, 5, 5]
  assert primeFactors(37) == [37]
output: def primeFactors(n):
      i = 2
      factors = []
      while i * i <= n:
          if n % i:
              i += 1
          else:
              n //= i
              factors.append(i)
      if n > 1:
          factors.append(n)
      return factors