First, the definition of natural numbers

Natural numbers are used to measure the number of things or to indicate the order of things. That is, the numbers represented by the numbers 0, 1, 2, 3, 4, ... representing the number of objects are called natural numbers, and natural numbers start from 0, one by one, forming an infinite group. Natural numbers are ordered and infinite. Divided into even and odd numbers, composite numbers and prime numbers.

Second, classification

1 can be divided into odd and even numbers according to whether it is even.

(1) Odd number: Numbers that are not divisible by 2 are called odd numbers.

(2) Even number: A number divisible by 2 is called even number. That is to say, except odd numbers, they are all even numbers.

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

2. According to the number of factors, it can be divided into prime number, composite number, 1 and 0.

(1) prime number: A natural number with only 1 and being a prime number is called a prime number. Also known as prime numbers.

(2) Composite number: A natural number that has other factors besides 1 and is itself a composite number is called a composite number.

(3) 1: only 1 factor. It is neither a prime number nor a composite number.

(4) Of course, 0 can't calculate the factor, just like 1, which is neither a prime number nor a composite number.

Note: This is a factor, not a divisor.