Even numbers are integers divisible by 2. Even numbers are also called even numbers. If a number is a multiple of 2, it is even and can be expressed as 2n; Otherwise, it is an odd number, which can be expressed as 2n+ 1(n is an integer), that is, the remainder of odd number divided by two is 1.

An odd number is an integer that is not divisible by 2. The mathematical expression is 2k+ 1. Odds can be divided into positive odd numbers and negative odd numbers.

Regarding even and odd numbers, there are the following properties:

(1) Two consecutive integers must be odd and even.

(2) The sum or difference between odd numbers is even; The sum or difference between even and odd numbers is odd; The sum of any number of even numbers is even; The sum of odd numbers is odd; The sum of even and odd numbers is even.

(3) The sum or difference of two odd (even) numbers is even; The sum or difference between even and odd numbers must be odd numbers.

(4) All positive even numbers except 2 are composite numbers.

(5) The greatest common divisor of adjacent even numbers is 2, and the least common multiple is half of their product.

(6) The product of odd number and odd number is odd number; The product of even number and even number is even number; The product of odd number and even number is even number.

(7) Even numbers must be 0, 2, 4, 6 or 8; Odd numbers must be 1, 3, 5, 7 or 9.

(8) Any odd number is not equal to any even number; The continuous product of several integers, if one of them is even, then the product must be even.

(9) Even squares are divided by 4, odd squares by 8, and the remainder is 1.