-18 is an even number.
-18 is a Harshad number, which means it is divisible by the sum of its digits (1 + 8 = 9, and -18 is divisible by 9).
In binary, -18 is represented as 1111111111111111111111111111111111111111111111111111111111101110.
In hex, -18 is represented as ffffffffffffffee.