Is there a function which can find all or part of the prime numbers?

today we don't have practical to find all prime number. you can find a part of them through Mersenne number: 2^p-1 or Fermat number: 2^(2^n) with p is prime number and n is nature number

a prime number is only devisible by 1 other number and 1
i am not sure for 100 % but i am sure 25%
still in school and learning about this

There is the Sieve of Eratosthenes and the Sieve of Atkin.