Divisors/Factors

[DCJ]

I've always thought of a factor as an integer that divides evenly into another integer

I read a definition that stated that for an integer N, a divisor is a POSITIVE integer that can divide N into another integer.

Divisors of 100: 100, 50, 25...

Why can't divisors be negative? (since 100 can be divided by -25 to yield -4)

[Ian Stewart]

Divisors can certainly be negative. On the GMAT, however, every divisibility question I've ever seen is restricted to positive integers only (the question will say 'positive divisors'), so it's very unlikely you'll need to be concerned about negative divisors on test day.

Out of curiosity, where did you read that definition of a divisor? It isn't correct.