Fastest Solution For Largest Prime Factor

Question

Is there a faster way to find the prime factors of 600851475143?

My computer still has not been able to produce an answer. Here's my code:

import sympy
num = 600851475143
list(filter(lambda x: sympy.isprime(x) and num % x ==0,range(2,600851475143 +1))

related: https://stackoverflow.com/q/31120986/4954037 and https://stackoverflow.com/questions/30553925/adding-wheel-factorization-to-an-indefinite-sieve/30563958#30563958 and many more... — hiro protagonist, May 07 '19 at 06:00
I think that there are more resources about this in http://codereview.stackexchange.com — Jean-François Fabre, May 07 '19 at 06:03
basically: compute primes up to sqrt(num), test divisors, then test if prime or if _other_ divisor is prime. — Jean-François Fabre, May 07 '19 at 06:04
@Jean-FrançoisFabre Thanks. I need a faster solution than mine as I still have not seen the solution on my computer — Don Cheeto, May 08 '19 at 01:20

score 0 · Answer 1 · answered May 22 '19 at 23:24

This returns instantly:

In [17]: import sympy                                                                                                             

In [18]: sympy.factorint(600851475143)                                                                                            
Out[18]: {71: 1, 839: 1, 1471: 1, 6857: 1}

So

In [19]: max(sympy.factorint(600851475143))                                                                                       
Out[19]: 6857

Fastest Solution For Largest Prime Factor

1 Answers1