To any set that contains it!
It belongs to {1.18},
or {45, sqrt(2), pi, 1.18, -3/7},
or all numbers between -2 and 453,
or improper fractions (1.18 = 19/50],
or rational numbers,
or real numbers,
or complex numbers,
etc.
No. One, a counting number, doesn't belong to either of those sets.
The complex numbers.
Counting numbers
The real numbers.
There are two sets of numbers listed at the bottom of a check. These sets of numbers are the routing numbers and the account number. The nine digit set of numbers is the routing number.
Rational numbers
There are no sets of three consecutive numbers totaling 118.
real numbers, irrational numbers, ...
Natural numbers.
It can be element of: Rational numbers or Real numbers
17 belongs to the set of prime numbers
1.18 is a number and number do not contain any sets (of any kind).
Irrational Numbers which are a subset of Real Numbers which are a subset of Complex Numbers ...
The rational numbers, the real numbers and sets of higher order which contain the reals such as the complex numbers.
-10 belongs to the set of all integers denoted by Z.
-28 belongs to: Integers, which is a subset of rationals, which is a subset of reals, which is a subset of complex numbers.
173 belongs to the set of positive natural numbers and it also belongs to the set of prime numbers.