Prime numbers are also called prime numbers, and there are infinite numbers. A natural number greater than 1 is called a prime number if it cannot be divided by other natural numbers (except 0) except 1 and itself; otherwise it is called a composite number. According to the fundamental theorem of arithmetic, every integer greater than 1 is either a prime number itself or can be written as the product of a series of prime numbers; and if the order of these prime numbers in the product is not considered, then the written form is unique.

In the field of natural numbers, prime numbers are indivisible numbers and are the basic elements that make up all natural numbers. For example, 10 is the product of 2 and 5. There are infinite prime numbers, so there are also infinite elements in the arithmetic world. All objects, theorems, and methods in the arithmetic world are composed of its basic elements, prime numbers.