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Old 2018-11-26, 13:56   #1
enzocreti
 
Mar 2018

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Default Curious prime
131071773869

I found this curious prime formed by the concatenation of Mersenne prime 131071 and another 6 digit prime 773869.

Any other prime like that? I mean can you find another prime which is the concatenation of 131071 and another 6 digit prime?
Last fiddled with by enzocreti on 2018-11-26 at 13:57
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Old 2018-11-26, 14:45   #2
firejuggler
 
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Apr 2010
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Quote:
Originally Posted by enzocreti View Post
131071773869

I found this curious prime formed by the concatenation of Mersenne prime 131071 and another 6 digit prime 773869.

Any other prime like that? I mean can you find another prime which is the concatenation of 131071 and another 6 digit prime?
11310711000133
11310711000151
11310711000397
11310711000409
11310711000691
11310711000763
11310711000889
11310711000907


to cite a few and a few more here
Last fiddled with by firejuggler on 2018-11-26 at 14:46
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Old 2018-11-26, 14:57   #3
enzocreti
 
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Default curious prime
It is not 113...but 1310...
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Old 2018-11-26, 15:14   #4
firejuggler
 
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my bad

1310711000099
1310711000171
1310711000381
1310711000483
1310711000723
1310711000777


and many more
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Old 2018-11-26, 15:15   #5
Dr Sardonicus
 
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Quote:
Originally Posted by enzocreti View Post
131071773869

I found this curious prime formed by the concatenation of Mersenne prime 131071 and another 6 digit prime 773869.

Any other prime like that? I mean can you find another prime which is the concatenation of 131071 and another 6 digit prime?
There are 4747 such primes.
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Old 2018-11-26, 17:21   #6
CRGreathouse
 
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Quote:
Originally Posted by Dr Sardonicus View Post
There are 4747 such primes.
There are 4572 for 2^19 - 1 = 524287 and 15986936 for 2^31 - 1 = 2147483647. The next Mersenne prime isn't doable (would require looping over > 2e17 primes).
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Old 2018-11-27, 02:45   #7
retina
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Quote:
Originally Posted by Dr Sardonicus View Post
There are 4747 such primes.
Which is itself a two-digit prime concatenated with a two-digit prime. OMG the coincidences are around! The primes are everywhere. I'm beginning to think that might be more than just a few, possibly infinite.
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