Two Primes = A 400 digit number

It seems that any number with 300 or more digits seems very hard to get. How can I find two prime numbers that if multiplied, I'll get a 400 digit number?

>>1

One computer + time = exhaustive search.  Note that you may be dead before the answer is found, but all science requires sacrifice.

100000929000001 * (2^1279 - 1) =
10408028884354591593
51465805683754600337
31896239083680656292
26432005396500315738
69961000470903971800
05285161232929230672
78085491011731825668
79138646005876890430
00738477599918129252
89474738359638417639
93017621142884424531
06799212965291026509
50864791348184303461
43522269271136681852
66159013266424636756
53730731056290654943
25888436080492240891
53424130264764090555
30399725712180111378
41863005024991729087

>>3
That second one being the largest prime known to be expessible as the form 2^x -1, correct?  I saw "proof," too.

>>4
no, that would be 2^25964951 − 1, about 7.8 million digits

Your equation is incorrect.

(2^11)-1 = 23*89

(2^11)-1 = 23x89

Your equation is incorrect.

>>7

Oh, so 2 to the power of 11 minus one equals to 23 multiplied by x multiplied by 89? Math notation sucks, get over it.

You know, I looked at both those equations for a couple minutes and couldn't for the life of me figure out what the difference was until >>8 pointed it out.

$brain =~ s/x/\*/;

When typing, I usually do x(y).  Same as x * y anyway.

>>6
>>7
>>8
>>9

what do any of your posts have to do with this thread?

the largest known primes are mersenne primes because they're all 1s.  2^n-1 is n-1 ones.  ie. 2^11-1 = 1111111111.  easy to work with on computers.

>>8
NO U
2^x-1 does not always = a prime number

This thread is fail. Compare your at a glance math skills to mine and kill yourselves.

bump

>>12
all ones...? in binary yes, i dont think the digits he's refering to are binary. but you are right, the mersenne primes are the place to look for the largest known primes.

>>10
Function x applied to argument y.

Also, three-year-old thread.