-9 is an odd number.
-9 is a Harshad number, which means it is divisible by the sum of its digits (9 = 9, and -9 is divisible by 9).
In binary, -9 is represented as 1111111111111111111111111111111111111111111111111111111111110111.
In hex, -9 is represented as fffffffffffffff7.