What does prime number mean?

A prime number is also called a prime number, which means "an integer greater than 1 can only be divisible by 1 and the number itself". A prime number can also be equivalently expressed as "a number that is greater than 1 and has only 1 and its own two divisors within a positive integer range".

The common prime numbers in middle school mathematics are less than 20: 2, 3, 5, 7, 1 1 3, 17, 19.

A summary of related knowledge of prime numbers;

1, the minimum prime number is 2, and the minimum composite number is 4. Note that the minimum prime number and the minimum composite number are even numbers.

2. Prime numbers greater than 2 are all odd numbers, and 2 is the only even number among prime numbers.

3. 1 is neither a prime number nor a composite number.

4. Positive integers greater than 1 are either prime numbers or composite numbers.

5. prime numbers are not all odd numbers, but even numbers, such as 2.

Calculation of the number of prime numbers:

1, there must be at least one prime number between a number greater than 1 and its twice (that is, within the interval (a, 2a)).

2. There is a prime arithmetic progression of any length.

3. An even number can be written as the sum of two composite numbers, and each composite number has at most 9 prime factors.

4. Even numbers must be written as prime numbers plus composite numbers, in which the number of factors of composite numbers has an upper bound.

5. Even numbers must be written as a prime number plus a composite number consisting of at most five factors. Later, someone shortened the result to (1+5).

6. A sufficiently large even number must be written as a prime number plus a composite number consisting of at most two prime factors. Short for (1+2).