## Re: [PrimeNumbers] One kind of prime numbers

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• Oh - read too hasty... Jud is right - nevertheless the palindromic primes are a proper subset of the reversible primes. :) Ronny
Message 1 of 6 , Apr 20, 2006
Jud is right - nevertheless the palindromic primes are a proper subset of
the reversible primes. :)

Ronny
• ... Two different names are used: emirp (prime backwards) and reversible prime . The definition usually excludes palindromes. The largest known are at
Message 2 of 6 , Apr 20, 2006
Jose C. Martinez wrote:

> I wanted to know how are called those primes numbers that when are
> readed from left to right and from right to left both number are
> primes.

Two different names are used:
"emirp" (prime backwards) and "reversible prime".
The definition usually excludes palindromes.

The largest known are at http://www.primepuzzles.net/puzzles/puzz_020.htm
(Only a few GHz days work).

This weeks puzzle is also about them:
http://www.primepuzzles.net/puzzles/puzz_357.htm

--
Jens Kruse Andersen
• ... 101, hmmmm - sounds totally tetradic to me! Phil () ASCII ribbon campaign () Hopeless ribbon campaign / against HTML mail / against
Message 3 of 6 , Apr 20, 2006
--- "Jose C. Martinez" <jcmtnez90@...> wrote:
> I wanted to know how are called those primes numbers that when are
> readed from left to right and from right to left both number are
> primes.
> For example
>
> 13-31
> 17-71
> 37-73
> 79-97
> 101-101

101, hmmmm - sounds totally tetradic to me!

Phil

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