Composite numbers can be divided into odd and even numbers, basic composite numbers (divisible by 2 or 3), negative composite numbers (6N- 1) and positive composite numbers (6N+ 1), two-factor composite numbers and multi-factor composite numbers.
One method of composite number is to calculate the number of prime factors. The sum of two prime factors is called semi-prime, and the sum of three prime factors is called wedge number. In some applications, composite numbers can also be divided into composite numbers of odd prime factors and composite numbers of even prime factors.
Extended data
If N+ 1 is a prime number, then N+ 1 is greater than p 1, p2, pn, so it is not in those assumed prime numbers.
If N+ 1 is a composite number, because any composite number can be decomposed into the product of several prime numbers; The greatest common divisor of n and N+ 1 is 1, so N+ 1 cannot be divisible by p 1, p2, pn, so the prime factor obtained by this complex decomposition is definitely not in the assumed prime set.
Therefore, whether the number is a prime number or a composite number, it means that there are other prime numbers besides the assumed finite number of prime numbers. So the original assumption doesn't hold water. In other words, there are infinitely many prime numbers.
Other mathematicians have given some different proofs. Euler proved by Riemann function that the sum of reciprocal of all prime numbers is divergent, Ernst Cuomo proved more concisely, and hillel furstenberg proved by topology.
Any natural number n greater than 1 can be uniquely decomposed into the product of finite prime numbers, where p 1
This decomposition is called the standard decomposition of n.
Baidu Encyclopedia-Composite Number (the basic concept of digital classification)