20110515, 02:58  #1 
May 2011
3_{10} Posts 
Semiprimes
Does anyone know where can I get a list of semiprime numbers (>123 decimal digits) with their corresponding prime factors?
Can anyone help me to factorise the following 123digit semiprime? 270670841438652918328457437265155619391032450133463282814465259139067145362144253227993241689950508665789547410822808227577 Many thanks. 
20110515, 04:43  #2  
Nov 2003
2^{2}·5·373 Posts 
Quote:
Quote:
You also need to explain why anyone should want to do your work for you. 

20110515, 08:49  #3  
Bamboozled!
"πΊππ·π·π"
May 2003
Down not across
2·3·1,753 Posts 
Quote:
Hian: here is a list for you: Code:
13672189887874844830294854600197645512844795863881883253689969830974172409049945718439475079482752818122343529516565272453 = 1496065788071742890012822928063153445784598021413069044090849 * 9138762477482175803233819882492079303177779082384971201704997 27193224269088935025333248735936824028463903074170155941135660729806618027705547104021063592551008779582473241244874916677 = 2975591535078494718909305165623136593204335955651117007329441 * 9138762477482175803233819882492079303177779082384971201704997 83516979619836155805053630304214506559429428372337994908795086403369674908014861010054485048573487229087697485079814770009 = 9138762477482175803233819882492079303177779082384971201704997 * 9138762477482175803233819882492079303177779082384971201704997 The answer to your other question is: yes. Paul 

20110515, 09:16  #4 
May 2011
3 Posts 
Thank you so much Paul, you are so helpful.
Actually, I have been searching for programmes from websites (as suggested by posts in this forum) which can help me to factorise semiprimes. However, I still can't get the answer after running the programmes continuously for almost 2 days. Two good websites I have found so far are: http://www.alpertron.com.ar/ECM.HTM http://sites.google.com/site/bbuhrow/home Is there any better suggestions? 
20110515, 11:07  #6  
Nov 2003
1110100100100_{2} Posts 
Quote:
BTW, a simple google search will turn up lots of RSA public keys.......... 

20110515, 11:15  #7  
Nov 2003
7460_{10} Posts 
Quote:
Code:
2 * 88625379503308113870163817479116818523025223399242215471800784810025248381387984608067747463864839726134410700901664118330633 3 * 88625379503308113870163817479116818523025223399242215471800784810025248381387984608067747463864839726134410700901664118330633 5 * 88625379503308113870163817479116818523025223399242215471800784810025248381387984608067747463864839726134410700901664118330633 7 * 88625379503308113870163817479116818523025223399242215471800784810025248381387984608067747463864839726134410700901664118330633 11 * 88625379503308113870163817479116818523025223399242215471800784810025248381387984608067747463864839726134410700901664118330633 13 * 88625379503308113870163817479116818523025223399242215471800784810025248381387984608067747463864839726134410700901664118330633 17 * 88625379503308113870163817479116818523025223399242215471800784810025248381387984608067747463864839726134410700901664118330633 19 * 88625379503308113870163817479116818523025223399242215471800784810025248381387984608067747463864839726134410700901664118330633 . . . . . 

20110515, 11:39  #8 
Dec 2010
Monticello
11100000011_{2} Posts 
What's the approximate runtime for the OP's number? (Knowing that the variance could be wide, no proof that it couldn't have a 10bit factor that could be found in under an hour by TF, ASSUMING its roughly P60*P63 )

20110515, 13:06  #9  
"William"
May 2003
New Haven
2^{3}·5·59 Posts 
Quote:
http://gilchrist.ca/jeff/factoring/n...ers_guide.html 

20110524, 02:46  #10 
Oct 2007
Manchester, UK
2×3×223 Posts 
If you want to factor this number then GNFS is the way to go, you could crack it open with ECM, but it'll take a lot longer since it has two 62 digit factors.

20110529, 07:11  #11  
May 2007
Kansas; USA
7×13×113 Posts 
Quote:
No that isn't a list. He asked for a list of semiprimes > 123 digits. These only have 122 digits. Bob's list is good though. BTW, the OP hasn't been on the forum since 1 day after his follow up response. I guess he wasn't very serious about learning about factoring. He obviously just wanted his work done for him. 

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