mersenneforum.org > Math Largest 64 bit prime?
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 2004-12-26, 19:33 #1 amcfarlane     Nov 2004 UK 2×19 Posts Largest 64 bit prime? Can anyone tell me please what the largest prime number is that will fit into a 64-bit unsigned variable?
 2004-12-26, 21:06 #2 Xyzzy     "Mike" Aug 2002 23·312 Posts Sounds like a homework problem! http://www.utm.edu/research/primes/l...mall/0bit.html
 2004-12-26, 21:12 #3 Xyzzy     "Mike" Aug 2002 170108 Posts Code: mv@k8:~$echo '2^64-59' | bc | factor 18446744073709551557: 18446744073709551557  2004-12-26, 21:20 #4 Xyzzy "Mike" Aug 2002 11110000010002 Posts Had I not cheated with that link, I would have done this: Code: #!/bin/sh counter=1 while [$counter != 1 ] do echo '2^64-'\$counter | bc | factor (( counter += 1 )) done
 2004-12-26, 21:26 #5 amcfarlane     Nov 2004 UK 2×19 Posts That's very clever ! -- Thanks...
 2004-12-26, 22:37 #6 marc     Jun 2004 UK 139 Posts Might want to set your while loop to != 0 or even just something like while [ " " ] and there's the obvious += 2 time saver.
 2004-12-26, 23:15 #7 alpertron     Aug 2002 Buenos Aires, Argentina 132210 Posts Just write b(2^64) in my factoring applet.

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