\(n!\) means \(n \times (n - 1) \times \cdots \times 3 \times 2 \times 1\).
For example, \(10! = 10 \times 9 \times \cdots \times 3 \times 2 \times 1 = 3628800\),
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 \(100!\).
Just like in Problem 16, the most efficient approach is to just calculate the number and sum its digits.
from math import factorial
p20 = lambda n=100: sum(map(int, str(factorial(n))))