if the opposite you are saying is the inverse, then the answer is no.
What exactly do you mean when you say "the opposite of a whole number" . . .
The set of whole numbers and their opposite is the same set.
The opposite of an even number is an odd number.
It's opposite is a negative. :P
They are a pair of opposite whole numbers. Except in the case of 0 whose additive opposite is itself and which does not have a mulitplicative opposite.
The square root of 16 is 4 which is a whole number.
technically speaking yes the opposite of 5 is -5
It would be 0, which is also its opposite.
Apart from zero (which is its own opposite), the opposites of whole numbers are also whole numbers. You have the set of whole numbers which is also known as the set of integers.