Integer Numbers
It can be defined as the number that can be written without a fractional (decimal) component.
Integers can be positive, negative, or 0.
From the numbers on the list only -4, 0, and 2 are integers. The rest of the numbers cannot be written without a decimal component.
For example:
-2/3 = -0.666
π = 3.14
The square root of 6 is 2.45
4.111... has an evident decimal component.
Answer: -4, 0, and 2