mersenneforum.org Today's Favorite Mega Number
 Register FAQ Search Today's Posts Mark Forums Read

2021-09-08, 10:06   #34
kruoli

"Oliver"
Sep 2017
Porta Westfalica, DE

10748 Posts

Quote:
 Originally Posted by MattcAnderson Check out this mega prime 1,753,961.
As you found out by yourself, 1,753,961 is not a prime. You only slightly missed a "mega prime" (1,753,963)!

Last fiddled with by kruoli on 2021-09-08 at 10:07 Reason: Added quotation.

2021-09-08, 16:34   #35
Dr Sardonicus

Feb 2017
Nowhere

23×5×112 Posts

Quote:
 Originally Posted by MattcAnderson Check out this mega prime 1,753,961.
Not only is the number (as previously pointed out) not prime, but "mega prime" is all too easily confounded with the term "megaprime," which denotes a prime with at least a million decimal digits.

2021-09-09, 02:09   #36
Dr Sardonicus

Feb 2017
Nowhere

23·5·112 Posts

Quote:
 Originally Posted by MattcAnderson Hi again all, My new favorite seven digit number is 9,999,999. 9,999,999 = 3*3*239*4649.
This brought to mind the following example illustrating the properties of the blocks of digits in the repeating decimals for k/p, k = 1 to p, p prime. Here, p = 239, a factor of 9999999. Since 239 divides 9999999, the repeating decimal for k/239, k = 1 to 238, has period 7. The blocks of digits may be further classified by the following 34 numbers:

[1004184, 2887029, 2050209, 1464435, 1046025, 1757322, 1255230, 1087866, 1506276, 3054393, 1380753, 1966527, 3765690, 2635983, 1882845, 1631799, 1422594, 1589958, 1129707, 4979079, 3556485, 3974895, 2426778, 4476987, 1213389, 2384937, 4560669, 1924686, 2803347, 2343096, 1673640, 1171548, 2008368, 4058577]

Each of these 34 numbers is the 7-digit block for the repeating decimal for a fraction k/239, for some k between 1 and 238. In each case, the value of k is obtained by dividing the 7-digit number by 41841. For example, dividing 1004184 by 41841 gives 24, and 24/239 = .10041841004184...

By cyclically permuting the digits in each block, the seven-digit blocks of the repeating decimals for the remaining fractions k/239, k = 1 to 238, are obtained.

For example, cyclically permuting the digits of the first block gives 0041841, and .00418410041841... = 1/239; permuting again, 10/239 = .04184100418410..., 100/239 = .41841004184100..., 44/239 = .18410041841004... and so on.

Each of the numbers is the smallest cyclic permutation of the block of digits whose leading digit is non-zero (i.e, a number between 1000000 and 9999999).

Last fiddled with by Dr Sardonicus on 2021-09-09 at 02:16 Reason: elaborate on permuting blocks of digits

 2021-09-09, 04:25 #37 MattcAnderson     "Matthew Anderson" Dec 2010 Oregon, USA 13×67 Posts Hi all, Today's mega number is 3,152,781 And due to a modern computer tool we can see that this number can be written as 3*3*137*2557. Matt Last fiddled with by MattcAnderson on 2021-09-09 at 04:28 Reason: oops mega number not mega prime
 2021-09-09, 13:30 #38 Uncwilly 6809 > 6502     """"""""""""""""""" Aug 2003 101×103 Posts 2·7·709 Posts There is no need for a modern computer to factor that number.
2021-09-09, 16:30   #39
Dr Sardonicus

Feb 2017
Nowhere

10010111010002 Posts

Quote:
 Originally Posted by Uncwilly There is no need for a modern computer to factor that number.
Especialy in light of (my emphasis)
Quote:
 Originally Posted by MattcAnderson Today's favorite Mega number is 7,122,222. And by inspection, we can see that the prime factorization is 2*3*3*3*131893.
If you can do that "by inspection" (and determining 131893 is prime by TF requires dividing 131893 by all primes up to about 360), I'd say 3152781 could also be done "by inspection."

 2021-09-15, 03:24 #40 MattcAnderson     "Matthew Anderson" Dec 2010 Oregon, USA 15478 Posts Hi all, Today's favorite mega number is 3,157,793. My computer tool, Maple, tells us that this number has a full prime factorization of 53*59581. Regards, Matt
 2021-09-16, 08:14 #41 MattcAnderson     "Matthew Anderson" Dec 2010 Oregon, USA 13×67 Posts Hi again all, Today's favorite mega number is 2,456,921. My computer has Maple software, so, with the ifactor() command, I can see this number has full prime factorization of 53*151*307. Regards, Matt
 2021-09-18, 05:20 #42 MattcAnderson     "Matthew Anderson" Dec 2010 Oregon, USA 87110 Posts Hi all, Today's favorite Mega number is 4,692,781. It's full prime factorization is 2677*1753. Regards, Matt
 2021-09-26, 17:40 #43 MattcAnderson     "Matthew Anderson" Dec 2010 Oregon, USA 13×67 Posts Hi again all, Today's favorite mega number is 9,876,567. The prime factorization of this number is 3*103*31,963. Have a nice day. Matt

 Similar Threads Thread Thread Starter Forum Replies Last Post ewmayer Lounge 31 2015-10-02 02:39 pepi37 Riesel Prime Search 5 2014-02-05 21:39 science_man_88 Science & Technology 3 2010-07-06 23:53 jasong jasong 1 2008-12-26 10:19 Joshua2 Hobbies 3 2007-09-01 19:50

All times are UTC. The time now is 18:04.

Sun Sep 26 18:04:24 UTC 2021 up 65 days, 12:33, 0 users, load averages: 1.61, 1.51, 1.46