Write a method that returns 'true' if the input parameter is a Harshad/Niven number and 'false' otherwise. HARSHAD/NIVEN NUMBER: A number that is divisible by the sum of its own digits. For example, 1729 is a Harshad number because 1 + 7 + 2 + 9 = 19 and 1729 = 19 × 91. More generally, a Harshad number, or Niven number in a given number base, is an integer that is divisible by the sum of its digits when written in that base. 2620 and 2924 are Harshad amicable pairs, since 2620 is divisible by (2 + 6 + 2 + 0) or 10, and 2924 is divisible by (2 + 9 + 2 + 4) or 17, since 2924 = 17 x 172.