Du mangler bare å plusse sammen alle tallene i 3628800, altså 3 + 6 + 2 + 8 + 8 + 0 + 0.
Lagde en ganske kort variant i Python (Python 2.6.6)
Kode
import math
n, i = 0, str(math.factorial(100))
for x in i: n+=int(x)
print n
Kode
import math
print sum([int(i) for i in str(math.factorial(100))])