I have a general problem with questions related to factors, multiples, remainders. I would appreciate if someone would share a simple strategy for solving such questions.

This question appeared in one preparation software and i dont understand the logic:

When 777 is divided by a positive integer n, the remainder is 77. how many possibilities are there for n?
2
3
4
5
6

What difficulty would this question be rated?

Appreciate your help.