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A friend told me that the number starting with 911 followed by 911 zeros ending with 119 (that is $911\cdot 10^{914}+119$) is a prime number, the so-called Porsche prime. Maple indeed confirms that this number is a prime.

Does anybody know how this prime number was discovered?

Joel Adler
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    Out of curiosity, why is it called the "Porsche" prime? – Vincent Jun 25 '16 at 22:15
  • Certainly possible. You should get someone to confirm primality with a program that gives a certificate, https://en.wikipedia.org/wiki/Primality_certificate – Will Jagy Jun 25 '16 at 22:40
  • @Vincent the Porsche 911 is their most famous flagship car, so the use of 911 and 119 here, makes it a possible homage to the car. – Sidharth Ghoshal Jun 25 '16 at 22:45
  • Also the Porsche 914 was another one of their cars too, so thats just a funny coincidence – Sidharth Ghoshal Jun 25 '16 at 22:45
  • Found the reference, the program was indeed called primo, and some of the people in this post know how to use it or install it: http://math.stackexchange.com/questions/402357/is-184720132-really-a-prime – Will Jagy Jun 25 '16 at 22:49
  • http://www.ellipsa.eu/public/primo/primo.html#Overview shows some times. It seems your number would take just a minute of waiting rather than a week. – Will Jagy Jun 25 '16 at 22:59
  • More interestingly described as "911" followed by 911 zeros, followed by the reverse of "911". It is a palindromic prime, and people have been amused by those for a long time, so perhaps first found as part of one of those searches. If one wanted to do so, a simple program finds probable primes of 911000..000119 to 1000 zeros, including this one, in under a second. Proving takes a little more time: check factordb (a few seconds), run Primo (under 1 minute), or run Pari/GP, ECPP-DJ, or other tools (a few minutes). – DanaJ Jun 25 '16 at 23:01

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