Even numbers can be divided evenly into groups of two. The number
four can be divided into two groups of two.

Odd numbers can NOT be divided evenly into groups of two. The
number five can be divided into two groups of two and one group of one.

Even numbers always end with a digit 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 a digit 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.

1Odd |
2Even |
3Odd |
4Even |
5Odd |
6Even |
7Odd |
8Even |
9Odd |
10Even |
11Odd |
12Even |

1Odd |
3Odd |
5Odd |
7Odd |
9Odd |
11Odd |

2Even |
4Even |
6Even |
8Even |
10Even |
12Even |