Even numbers can be separated evenly into groups of 2. The number four can be separated into 2 groups of 2.
Odd numbers can NOT be separated evenly into groups of 2. The number five can be separated into 2 groups of 2 and one group of one.
Even numbers always end with an any number 0 to 9 of 0, 2, 4, 6 or 8. 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30 are even numbers.
Odd numbers always end with an any number 0 to 9 of 1, 3, 5, 7, or 9. 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31 are odd numbers.