What number is its own additive inverse?

The number that is its own additive inverse is zero. This means that when you add zero to itself, the result is still zero (0 + 0 = 0). In mathematical terms, an additive inverse of a number ( x ) is a number ( -x ) such that ( x + (-x) = 0 ), and for zero, it holds true that ( 0 + 0 = 0 ). Thus, zero is the only number that is its own additive inverse.