Final answer:
The number -√81 is a negative real number.
Step-by-step explanation:
The number -√81 is a real number.
-√81 represents the square root of 81, which is 9. Since the square root of a positive number is always positive, the square root of 81 is 9. However, the negative sign in front of the square root indicates that the number is negative, so the answer is -9. Therefore, -√81 is a negative real number.