Of many prime number tests floating around the Internet, consider the following Python function: Since all primes > 3 are of the form 6n ± 1, once we eliminate that n is: not 2 or 3 (which are prime) and not even (with n%2) and not divisible by 3 (with n%3) then we can test … Read more
You need to check all numbers from 2 to n-1 (to sqrt(n) actually, but ok, let it be n). If n is divisible by any of the numbers, it is not prime. If a number is prime, print it. You can write the same much shorter and more pythonic: As I’ve said already, it would … Read more
I’m trying to do a simple primality test in Python. Accoding to Wikipedia, a primality test is the following: Given an input number n, check whether any integer m from 2 to n − 1 divides n. If n is divisible by any m then n is composite, otherwise it is prime. I started with … Read more
Of many prime number tests floating around the Internet, consider the following Python function: Since all primes > 3 are of the form 6n ± 1, once we eliminate that n is: not 2 or 3 (which are prime) and not even (with n%2) and not divisible by 3 (with n%3) then we can test … Read more
There are some problems: Why do you print out count when it didn’t divide by x? It doesn’t mean it’s prime, it means only that this particular x doesn’t divide it continue moves to the next loop iteration – but you really want to stop it using break Here’s your code with a few fixes, it prints … Read more
A pretty simple and concise brute-force solution to check whether a number N is prime: simply check if there is any divisor of N from 2 up to the square root of N (see why here if interested). The following code is compatible with both Python 2 and Python 3: And here’s a simpler Python 3 only … Read more
Two part question: 1) Trying to determine the largest prime factor of 600851475143, I found this program online that seems to work. The problem is, I’m having a hard time figuring out how it works exactly, though I understand the basics of what the program is doing. Also, I’d like if you could shed some … Read more