The number that fits into all the following number sets: natural number, whole number, and integer is 8.
- Natural numbers are positive integers (1, 2, 3, ...).
- Whole numbers are non-negative integers (0, 1, 2, 3, ...).
- Integers include positive and negative whole numbers, as well as zero (..., -2, -1, 0, 1, 2, ...).
The number 8 is a positive integer, thus it fits into all these categories.