20101231, 21:40  #1 
Einyen
Dec 2003
Denmark
3,037 Posts 
Happy Prime Year MMXI!
Still about 1h20min until new year here in Denmark, but I'm posting before the fireworks.
2011 is a prime year! 2^{2011}1 has 2 factors: http://www.mersenne.org/report_expon...&B1=Get+status 2011 = 7^{2}+21^{2}+39^{2} = 9^{2}+29^{2}+33^{2} = 9^{2}+9^{2}+43^{2} = 21^{2}+27^{2}+29^{2} 2011 = 2^{8}+3^{3}+12^{3} 3 natural disasters "predicted" for 2011 in various fiction: http://www.virtuescience.com/2011.html Other real world upcoming events: http://en.wikipedia.org/wiki/2011 http://www.imdb.com/year/2011/ 
20101231, 22:57  #2  
Account Deleted
"Tim Sorbera"
Aug 2006
San Antonio, TX USA
10253_{8} Posts 
Quote:
http://factordb.com/index.php?query=M2011 The cofactor is a 558 digit composite number. Not too likely to be fully factored for quite a while. 

20110101, 05:59  #3 
1976 Toyota Corona years forever!
"Wayne"
Nov 2006
Saskatchewan, Canada
5·911 Posts 
1 minutes to go here.....
count down with me....

20110101, 07:36  #4 
"Lucan"
Dec 2006
England
1100101001010_{2} Posts 

20110101, 08:04  #5 
Bemusing Prompter
"Danny"
Dec 2002
California
2×7×13^{2} Posts 
Unfortunately, 2010 was a dry year, in the context of new Mersenne primes. Let's hope that 0b11111011011 will really be a "prime" year!

20110101, 08:28  #6  
"Lucan"
Dec 2006
England
2·3·13·83 Posts 
Quote:
FLT? David 

20110101, 09:21  #7 
Mar 2010
On front of my laptop
1110111_{2} Posts 

20110101, 12:29  #8 
Account Deleted
"Tim Sorbera"
Aug 2006
San Antonio, TX USA
10AB_{16} Posts 
I'm not sure exactly what math is behind it, and it can probably vary depending on the program used to find the other factor, but some sort of PRP test is (AFAIK) most commonly used to show whether a cofactor in factoring (including Mersennes) is PRP or composite. A PRP test of such a small number is quite easy. PARI/GP can do it (with ispseudoprime; I think it would see that it's a base 2 RabinMiller PRP, then see that it's not a Lucas PRP) in ~50 ms on my computer.
Last fiddled with by MiniGeek on 20110101 at 12:41 
20110101, 16:05  #9  
"Lucan"
Dec 2006
England
2×3×13×83 Posts 
Quote:
David PS Does PRP = "Probably Prime"? If so, what does the R stand for  "robably"? Last fiddled with by davieddy on 20110101 at 16:12 

20110101, 16:35  #10 
Jun 2003
2221_{8} Posts 
[QUOTE=davieddy;244241]PS Does PRP = "Probably Prime"?
It means "probable prime", which is a technical term meaning a number which passes one of certain designated tests. It does not mean "probably prime". 1105 is a probable prime to many bases. (It's a Carmichael number.) But it's not probably prime. It's definitely composite. 
20110101, 16:39  #11 
"Lucan"
Dec 2006
England
2×3×13×83 Posts 
To raise another chestnut (from the dead?)
...from either 10 or 11 years ago,
Happy 202nd decade to y'all David Last fiddled with by davieddy on 20110101 at 16:40 
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