There are infinite prime numbers, also called prime numbers. A natural number greater than 1 cannot be divisible by other natural numbers except 1 and itself, in other words, this number has no other factors except 1 and itself; Otherwise it is called a composite number.

According to fundamental theorem of arithmetic, every integer greater than 1 is either a prime number itself or a product of a series of prime numbers; If the order of these prime numbers in the product is not considered, then the writing form is unique. The smallest prime number is 2.