def test_sum_digits(self):
self.assertEqual(mathhelper.sum_digits(-1), 1)
self.assertEqual(mathhelper.sum_digits(0), 0)
self.assertEqual(mathhelper.sum_digits(1), 1)
self.assertEqual(mathhelper.sum_digits(2), 2)
self.assertEqual(mathhelper.sum_digits(21), 3)
self.assertEqual(mathhelper.sum_digits(867), 21)
self.assertEqual(mathhelper.sum_digits(99000009), 27)
def problem20():
""" Factorial digit sum
Find the sum of the digits in the number 100!
"""
return mathhelper.sum_digits(math.factorial(100))
def problem16():
""" Power digit sum
What is the sum of the digits of the number 2^1000?
"""
return mathhelper.sum_digits(2 ** 1000)
