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, ...).
- Integers include all whole numbers and their negative counterparts (..., -3, -2, -1, 0, 1, 2, 3, ...).
Since 8 is a positive integer, it fits into all three categories.