What are harshad numbers?

Answer 1

I asked Google the question, I was expecting the website that claims to have the answer to actually have an answer.

All I know is I keep getting junk phone calls from phone numbers all over, and most of the time when I Google search the phone number, I find some stupid page that lists large blocks of phone numbers sequentailly. Some of those numbers are color coded to indicate they are a harshad number, which apparently is a mathematical concept.

What I cannot figure is why the digits comprising a telephone number would benefit from having some mathematical significance. Seems quite bizare to me.