Re: prime numbers and African artifact

Florian Rudolph (uzs18d@ibm.rhrz.uni-bonn.de)
Sun, 16 Jul 1995 09:19:45 GMT

martin@melon.wdg.uk.ibm.com (Martin Bright) wrote:

>Peter Seebach (seebs@solutions.solon.com) wrote:
>|> > What's the easy way to show that 254365465431652436514232 is not
>|> >prime again?

>|> Simple!

>|> 2 + 5 + 4 + 3 + 6 + 5 + 4 + 6 + 5 + 4 + 3 + 1 +
>|> 6 + 5 + 2 + 4 + 3 + 6 + 5 + 1 + 4 + 2 + 3 + 2 = 91

>|> 9 + 1 = 10.

>|> 1 + 0 = 1.

>|> 1 is not a multiple of three, so the whole number is not a multiple of
>|> three, so it must be prime!

>Also the first two digits aren't divisible by 4, so the whole number isn't
>divisible by 4. This proves again that it is prime.

>Martin

Martin, I'm sorry, but I'm afraid you got it all wrong. The first two
digits aren't _multiplicable_ by 4 (because 25*4=100, and how should
that fit into the first two digits?). So the whole number isn't
multiplicable by 4. That's what proves that 254365465431652436514232
is indeed a prime.

Florian
"I did not, however, commit suicide, because I wished to know more of
mathematics." -- Bertrand Russell