#### Question Q2.7.3

A Harshad number is an integer that is divisible by the sum of its digits (for example, 21 is divisible by $2+1=3$ and so is a Harshad number). Correct the following code which should return True or False if n is a Harshad number or not respectively:

def digit_sum(n):
""" Find the sum of the digits of integer n. """

s_digits = list(str(n))
dsum = 0
for s_digit in s_digits:
dsum += int(s_digit)


When run, the function is_harshad raises an error:
>>> is_harshad(21)