20040618, 07:34  #1 
953 Posts 
How to check if a number is a Mersenne prime ?
What do I do if I think I have found a greater mersenne but my calculator has no way to check it, or I don't. (It can only do 2^400 or something...)
Is there a fairly easy way to check whether I have one or not with a program? I tried downloading 'ntprime' but I don't know how it works, it didn't seem to do anything... 
20040618, 09:20  #2 
Dec 2003
Paisley Park & Neverland
B9_{16} Posts 
A Mersenne number (> just check if the exponent is prime) or a Mersenne prime? For the latter: download Prime95 Version 23.8 from http://www.mersenne.org/freesoft.htm and enter the exponent in [Prime95]>[Advanced]>[Test]. If you don't see immedite progress just lower the entry in [Prime95]>[Options]>[Preferences]>[Iterations between screen outputs].
Prime95 works for exponents up to 79 300 000. MrHappy. 
20040618, 13:37  #3  
6809 > 6502
"""""""""""""""""""
Aug 2003
101×103 Posts
10010100001001_{2} Posts 
You can find a list of all known Mersenne primes here: http://www.utm.edu/research/primes/m...dex.html#known
Also, know that: Quote:


20040618, 16:14  #4 
2^{3}×653 Posts 
that's what u think!!

20040618, 20:40  #5 
Sep 2003
Borg HQ, Delta Quadrant
2·3^{3}·13 Posts 
I think our tests are fairly conclusive. We keep testing the exponent until we get two matching residues. Version 23 implements error codes so we can tell if a test is probably bad.

20040618, 20:55  #6 
6809 > 6502
"""""""""""""""""""
Aug 2003
101×103 Posts
19×499 Posts 
Yes, I think that the matching residues is key here. To have these 2 large numbers to happen to match and one be an erroneous test is highly unlikely. To have 2 that have errors that match is so unlikely that it is considered to be all but magical. The actual chances are around.
Having a second type of hardware with a second program check this with the same residue is considered proof for the math community. 
20040619, 08:18  #7 
2^{2}·7^{2}·19 Posts 
Ok I had the wrong program before, that one worked, thanks.
I was attemptimng one much higher than 8 mil, more like 54 million or something but it wasn't even a prime number so no luck... Thanks anyway. 
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