
Preparation 
Just what you need to know ! 
Integers, Natural Numbers and Whole Numbers
The numbers {... −4, −3, −2, −1, 0, 1, 2, 3, 4, ...} form the set of integers.
The notation { } indicates 'set' or collection, and the three dots indicate that the list continues endlessly to infinity.
The numbers {1, 2, 3, 4, ...} form the set of positive integers (also called natural numbers or counting numbers).
The numbers {−1, −2, −3, −4, ...} form the set of negative integers.
The number 0 is an integer which is neither positive nor negative. It is usually not considered a counting number.
The numbers {0, 1, 2, 3, 4, ...} form the set of whole numbers.
GMAT Math Review  Arithmetic : Index for Integers & Numbers
GMAT Math Review  Arithmetic : Practice Exercise for Integers & Numbers

