[Blindmath] new member... with a question!

[Alex Hall]

Hi all,
My name is Alex. I am in college for computer science, in my third year. In 
reading the description of this list I realize that the below is not quite 
in keeping with the usual topics on this list, however I am hoping that 
someone on here can point me to a list which would better suit my question. 
Here goes...

I am working on the problems at http://www.projecteuler.net and am on 
problem 3, which asks for the highest prime factor of some very large number 
(over six hundred billion). I am writing a small program to give me the 
answer, however the number is too large to (A) be stored in the usual 
variable type or (B) return an answer in anything approaching a fast time 
(if I use the old "try them all" method by dividing every number up to n/2 
into n and seeing if the result is 0, my time will be n/2-2). I tried 
getting the square and factoring that, but the square is a decimal that 
looks infinite. I know some numbers lend themselves to being prime-factored 
by getting the square root of the square above the number then finding the 
gcf of the number and the square root +1 and minus 1, but this does not work 
for all numbers and I am not sure what the trick to figuring out if it will 
work or not is.
So... is there a fast (ish) way to factor some number that is well over 
three hundred billion? I use JAWS, so an explanation in words supported by 
math, instead of all math symbols, would be great. As I said at the 
beginning of this message, I expect that this question is not what this list 
is for, but I hope that asking it will tell people what kind of list I am 
looking for and, if they know of one, they can tell me what it is. Thanks 
for any help!


Have a great day,
Alex
New email address: mehgcap at gmail.com