Problem 19

Factorial digit sum

Problem 21

Factorial digit sum

Problem 20

n! means n × (n − 1) × ... × 3 × 2 × 1
For example, 10! = 10 × 9 × ... × 3 × 2 × 1 = 3628800,
and the sum of the digits in the number 10! is 3 + 6 + 2 + 8 + 8 + 0 + 0 = 27.
Find the sum of the digits in the number 100!
from tools import factorial

def run():
    return reduce(lambda x, y: int(x) + int(y), str(factorial(100)))