Quicker way to write code/execute function faster for higher numbers?

Question

https://code.sololearn.com/cG4q5v7LqMBJ/?ref=app

Answer 1

In your isPrime function, you only need to check divisibility up to the square root of n, not up to n itself. You should also only be checking odd numbers. (Increasing loop by 2).

I've never done python before but I believe it would look something like this:
for i in range(3, int(n**(0.5)), 2)

That will improve that functions computing speed by about 10x.

Answer 2

In addition to limit testing to square root of tested number, you can store previous calculated primes number, and test divisibility only for primes ^^ ( it will drastically increase speed test for many testing number -- but not for only one ^^ )

Answer 3

That is exponentially faster. Thank you!