Project Euler Problem#20

#python program to sum the digits of factorial of a number
fac_num=1
def fac(num):
        global fac_num
        if num==1:
            return fac_num
        else:
            fac_num*=(num)
            return(fac(num-1))
def fac_sum(num):
    global fac
    fac=fac(num)
    sum=0
    for i in str(fac):
        sum+=int(i)
    return sum
print(fac_sum(100))  #648