The number of digits of a natural number is called the number of digits. One digit is one digit, two digits are two digits, three digits are three digits, and n digits are n digits.

Natural numbers can be divided into odd numbers and even numbers according to whether they are even numbers. Numbers that are not divisible by 2 are called odd numbers. A number divisible by 2 is called an even number. That is to say, except odd numbers, they are all even numbers.

0 is an even number. In 2002, the International Mathematical Association stipulated that zero was an even number, and in 2004, China also stipulated that zero was an even number. Even numbers can be divisible by 2, and so can 0, but numbers are still 0.

Natural numbers play a great role in daily life, and people use them widely. People often use natural numbers to mark or classify things, such as bus routes, house numbers, postal codes, etc.

Properties of natural numbers

1, orderly. The orderliness of natural numbers means that natural numbers can be arranged into a series starting from 0, without repetition or omission: 0, 1, 2, 3, which is called natural number series.

2. Infinite. Natural number set is an infinite set, and the sequence of natural numbers can be written endlessly.

3. Transitivity: Let n 1, n2 and n3 be natural numbers, if n1>; N2, n2 & gtN3, then n1>; n3 .

4.Trigement: For any two natural numbers n 1, n2, there exist and only exist the following three relationships: n1> N2, n 1=n2 or n 1.

5. Least number principle: There must be a minimum number in any nonempty set of natural number set. A set of numbers with properties of 3 and 4 is called a linear ordered set.