Prime number tests

To: cypherpunks@toad.com
Subject: Prime number tests
From: nobody@shell.portal.com
Date: Tue, 12 Apr 1994 18:37:07 -0700
Comments: This message is NOT from the person listed in the Fromline. It is from an automated software remailing service operating atthat address. Please report problem mail to <hfinney@shell.portal.com>.
Sender: owner-cypherpunks@toad.com

Well, there is one prime number test which NEVER fails, and that is that
(n-1)!+1 mod n is zero for all primes, and non-zero for all non-primes.
;-)