# Primality Test Formula

#### topsquark

##### Well-known member
MHB Math Helper
We can determinate if one number is prime with the modulo operation.
Primality Test Formula
Interesting. However I find the usual sieve of Erastothenes to be simpler and less time consuming. (I believe that the two methods are related to each other anyway.)

-Dan

#### Hugo1177

##### New member
I am not an expert in computational time, are you sure that the sieve is better for big numbers? I hear that there aren´t a efficient form to determinate if a number is prime or not in polynomial time. Here you only have to do the 30th or 40th derivative and divide one number relatively big by other

#### topsquark

##### Well-known member
MHB Math Helper
I am not an expert in computational time, are you sure that the sieve is better for big numbers? I hear that there aren´t a efficient form to determinate if a number is prime or not in polynomial time. Here you only have to do the 30th or 40th derivative and divide one number relatively big by other
I'm not an expert either. I'm simply guessing that taking derivatives is more time consuming than doing the sieve. I admit I may be wrong.

-Dan