The given number is,
Integer
Yes. Since -15 has no decimal part. It must be an integer.
Whole Number
No. The set of the whole number does not include negative numbers. So -15 cannot be a whole number.
Natural number
No. The set of natural numbers does not include negative numbers. So, -15 cannot be a natural number.
Irrational Number
No. Since -15 can be written in the form p/q, so the number -15 is rational and hence, cannot be an irrational number.