Update problem3.py

The prime factors of 13195 are 5, 7, 13 and 29.

What is the largest prime factor of the number 600851475143 ?


my algo:
Get all factors of a number num(in a list in ascending order)
Now scan the list in reverse order if the factor is prime or not(check divisibility by 2 to num-1)
The moment a factor is prime its the largest prime factor.