Integers

Integers are all of the counting numbers. They are represented by "I" i.e.
....,-3,-2,-1,0,1,2,3.....

They may be positive or negative. Integers that are multiples of 3 are called as even numbers or integers. Moreover 0 is also called as an even number/integer e.g.....,-6,-4,-2,0,2,4,6,......

The numbers other than these are odd integers.

Remainder is that integer which remains at the end of division of one number by another.

(This article give some study about the numbers in GRE preparation)
Further Reading:
Cracking the GRE, 2010 Edition (Graduate School Test Preparation)

Kaplan GRE Exam Vocabulary in a Box

Barron's GRE

Essential Words for the GRE (Barron's Essential Words for the GRE)