## Number 19

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• Is this an expected property of the number 19 or even 9? 19 digits 9191919191919191919 = 3 * 3 * 1021324354657687991 which has the digits n n-1 n+1 repeating
Message 1 of 5 , Sep 9, 2010
Is this an expected property of the number 19 or even 9?

19 digits 9191919191919191919 = 3 * 3 * 1021324354657687991

which has the digits n n-1 n+1 repeating as follows:

= 9 * (n n-1 n+1 (n+1) (n+1)-1 (n+1)+1 ...) / 10

Also note:
23 digits 91919191919191919191919 is prime

17 digits 91919191919191919 is prime.

11 digits 91919191919 is prime.

9 digits 919191919 is prime.

3 digits 919 is prime.

Ali
Prime numbers are God's signature!
www.heliwave.com

[Non-text portions of this message have been removed]
• ... The next probable prime has 25229 digits: (91*10^25229-19)/99 is Fermat and Lucas PRP! (166.8607s+0.0024s) David
Message 2 of 5 , Sep 10, 2010
<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 3 of 5 , Sep 10, 2010
>
>
> > 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 4 of 5 , Sep 10, 2010
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