a composite number, also known as a composite number, is a positive integer that satisfies any of the following (equivalent) conditions among positive integers greater than 1:

1. it is the product of two integers greater than 1;

2. have at least three positive factors (factors);

3. a non-prime number with at least one prime factor.

4. the product of two or more prime numbers can form a composite number, and only one composite number can be formed. conversely, a composite number can be split into the product of a set of prime numbers, and only into the product of a set of prime numbers.

5. any positive integer other than 1 that is not a prime number is a composite number.

, in addition to 1 and itself, there are other numbers with positive factors

note: "0" and "1" are neither prime numbers nor composite numbers.

a natural number that has only two positive factors, 1 and itself, is called a prime number (or prime number). (for example: from 2÷1=2, 2÷2=1, it can be seen that the factors of 2 are only two divisors: 1 and 2 itself, so 2 is a prime number. the opposite is a composite number: "except for 1 and 2 in addition to its two factors, there are also numbers with other factors are called composite numbers. for example: 4÷1=4, 4÷2=2, 4÷4=1. obviously, in addition to the two factors 1 and 4 itself, there are other factors of 4. the factor is 2, so 4 is a composite number.)

prime numbers within 100 are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83 , 89, 97, there are 25 prime numbers within 100.