20210808, 08:48  #254 
Romulan Interpreter
Jun 2011
Thailand
2×3×7×233 Posts 
Aren't mersenne prime palindromes themselves?

20210808, 09:04  #255 
Sep 2002
Database er0rr
5·773 Posts 
I base 2 they are. In fact any n>1 is a palindrome in base n+1 and in base n1
Last fiddled with by paulunderwood on 20210808 at 09:10 
20210808, 14:07  #256 
"99(4^34019)99 palind"
Nov 2016
(P^81993)SZ base 36
2^{4}·191 Posts 
All primes p not in https://oeis.org/A016038 are palindromes in some base < p1

20210911, 08:21  #257 
Sep 2002
Database er0rr
5·773 Posts 
Congrats to Serge and Ryan for the two smallest known Mega primes, prove with CHG at 28.7% factored of N+1
10^999999  1022306*10^287000  1 10^999999  1087604*10^287000  1 
20210911, 10:44  #258  
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
2×3×5×11×29 Posts 
Quote:
(The second one was found before search was called off, an incidental finding. ) Code:
... 10^999999+308267*10^292000+1 P 1000000 Batalov 02/2021 10^999999+593499 PRP 1000000 Peter Kaiser 02/2013 10^999999 C 1000000  a composite, smallest milliondigit number 10^999999172473 PRP 999999 Patrick De Geest 12/2016 10^9999991022306*10^2870001 P 999999 Propper,Batalov 09/2021 10^9999991087604*10^2870001 P 999999 Propper,Batalov 09/2021 ... 

20210911, 16:50  #259 
Jun 2015
Vallejo, CA/.
3·337 Posts 
Of course all repunits are “palindromes” per se, but in practical terms when a prime is a Mersenne, a Generalized Mersenne ( to other bases ), repunits, generalized repunits, they are not counted as palindromes in the database of “The primePages”

20210912, 17:20  #260 
Sep 2002
Database er0rr
5×773 Posts 
Congrats to Marc Wiseler and PrimeGrid for the "321" prime 3*2^177480341 (5,342,692 decimal digits) ranked as the 18th largest known prime.

20210912, 17:22  #261  
Sep 2006
The Netherlands
3×257 Posts 
Quote:


20210914, 20:08  #262 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
2·3·5·11·29 Posts 
Another Riesel "other" number is coming soon.
It is a palindrome, chock full of "9"s (with a few others) and is neatly 1,234,567 decimal digits long 
20210914, 21:01  #263 
Sep 2002
Database er0rr
5×773 Posts 
I am looking forward to its revelation. The largest palindrome before this one had 490,001 digits. So 1,234,567 digits is quite amazing considering its crunching is done with generic modular reduction.

20210915, 07:15  #264  
"99(4^34019)99 palind"
Nov 2016
(P^81993)SZ base 36
2^{4}·191 Posts 
Quote:
id 132704 and 132705 are palindromes. 

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