It belongs to an infinite number of sets.
For example the sets of:
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Irrational and transcendental
fractions
Any set of numbers that contain them! For example, they belong to the set {10, 11} or {10, 11, sqrt(2), pi, -3/7}, or {10, 11, bananas, France, cold} or all whole numbers between 3 and 53, or counting numbers, or integers, or rational numbers, or real numbers, or complex numbers, etc.
Integers. (This includes negative whole numbers.)
The integers. Also: the rational numbers, the real numbers and (depending on your definition) the complex numbers.