## Re: Number 19

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• ... The next probable prime has 25229 digits: (91*10^25229-19)/99 is Fermat and Lucas PRP! (166.8607s+0.0024s) David
Message 1 of 5 , Sep 10 4:58 AM
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<alipoland@...> wrote:

> 23 digits 91919191919191919191919 is prime

The next probable prime has 25229 digits:

(91*10^25229-19)/99 is Fermat and Lucas PRP! (166.8607s+0.0024s)

David
• ... and was found by Patrick de Geest in july 2004: http://www.primenumbers.net/prptop/searchform.php?form=%3F%2F99 Lélio [Non-text portions of this message
Message 2 of 5 , Sep 10 5:20 AM
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>
>
> > 23 digits 91919191919191919191919 is prime
>
> The next probable prime has 25229 digits:
>
> (91*10^25229-19)/99 is Fermat and Lucas PRP! (166.8607s+0.0024s)
>
> David
>
>
>

and was found by Patrick de Geest in july 2004:

Lélio

[Non-text portions of this message have been removed]
• ... According to Patrick de Geest s website, Hans Rosenthal found it. http://www.worldofnumbers.com/undulat.htm#supp919 Factorizations of (91*10^(2n+1)-19)/99
Message 3 of 5 , Sep 10 6:19 AM
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On 2010/09/10 21:20, Lélio Ribeiro de Paula wrote:
>>
>> The next probable prime has 25229 digits:
>>
>> (91*10^25229-19)/99 is Fermat and Lucas PRP! (166.8607s+0.0024s)
>
> and was found by Patrick de Geest in july 2004:
>

According to Patrick de Geest's website, Hans Rosenthal found it.
http://www.worldofnumbers.com/undulat.htm#supp919

Factorizations of (91*10^(2n+1)-19)/99 are here:
http://www.asahi-net.or.jp/~kc2h-msm/mathland/aba/aba919.htm

• ... The 15 digit number 151515151515151 is prime, too ; and it is the only such prime (undulating : aba...ba with ab = 10*a+b or ba = 10*b+a digits. M.
Message 4 of 5 , Sep 10 10:11 AM
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> 23 digits 91919191919191919191919 is prime
> 17 digits 91919191919191919 is prime.
> 11 digits 91919191919 is prime.
> 9 digits 919191919 is prime.

The 15 digit number 151515151515151 is prime, too ;
and it is the only such prime (undulating : aba...ba
with ab = 10*a+b or ba = 10*b+a digits.

M.
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