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A number divisible by 2 is even, and a number divisible by 2 is odd.

Even numbers can be represented by 2k, and odd numbers can be represented by 2k+ 1, where k is an integer.

Definition of even number:

1. In an integer, a number divisible by 2 is called an even number.

A multiple of two is called an even number.

3. Goldbach conjecture shows that any even number greater than two can be written as the sum of two prime numbers, but no one has proved this conjecture yet.

Odd number definition:

Among integers, numbers that are not divisible by 2 are called odd numbers. In daily life, people usually call odd numbers singular, as opposed to even numbers. Odd numbers can be divided into positive and negative odd numbers.

All integers are either odd or even. If a number is a multiple of 2, it is even (even), which can be expressed as 2n; Otherwise, it is odd (singular), which can be expressed as 2n+ 1(n is an integer), that is, the remainder of odd (singular) divided by two is 1.

In decimal system, you can judge whether the number is odd (singular) or even (even) by looking at the single digits: 1, 3, 5, 7 and 9 are odd (singular); Numbers with digits 0, 2, 4, 6 and 8 are even (even).

In China culture, it occasionally means "one pair, one pair, reunion". In ancient times, it was thought that even numbers were good and odd numbers were bad. So bad luck is called "uneven".