Integer
An integer is one of the numbers obtained in counting positive integers (also known as natural numbers): 
, zero: 
, or one of the negative integers: 
. If 
and 
are integers, then their sum 
, their difference 
, and their product 
are all integers, but their quotient 
may or may not be an integer.
The class of integers is the simplest class of numbers and is used to construct other classes like rational numbers and real numbers. The set of integers is symbolically written as 
.
