Largest 64 bit prime?
 

Can anyone tell me please what the largest prime number is that will fit into a 64-bit unsigned variable?

Sounds like a homework problem!

[url]http://www.utm.edu/research/primes/lists/2small/0bit.html[/url]

:innocent:

[code]mv@k8:~$ echo '2^64-59' | bc | factor
18446744073709551557: 18446744073709551557[/code]:smile:

Had I not cheated with that link, I would have done this:

[code]#!/bin/sh
counter=1
while [ $counter != 1 ]
do
echo '2^64-'$counter | bc | factor
(( counter += 1 ))
done[/code]

That's very clever ! -- Thanks...

Might want to set your while loop to != 0 or even just something like while [ " " ] and there's the obvious += 2 time saver.

Just write b(2^64) in [URL=http://www.alpertron.com.ar/ECM.HTM]my factoring applet[/URL].