- View SourceFor those not familiar with Wilson's Theory: P is a prime number if,

and only if, (P-1)! + 1 is divisible by P.

Now take the number 1, (1-1)! + 1 = 0! + 1 = 2.

2 is divisible by 1, so why isn't 1 prime? - View SourceHere is the definition of Wilson's Theorem from the Prime Pages:

http://www.utm.edu/research/primes/notes/proofs/Wilsons.html

Wilson's Theorem.

Let p be an integer greater than one. p is prime if and only if (p-1)! = -1 (mod p).

You seem to have left out the first part.

Tom Hadley

-----Original Message-----

From: paxtontravis [mailto:paxtontravis@...]

Sent: Tuesday, March 01, 2005 11:06 AM

To: primenumbers@yahoogroups.com

Subject: [PrimeNumbers] Wilson's Theory and the number 1

For those not familiar with Wilson's Theory: P is a prime number if,

and only if, (P-1)! + 1 is divisible by P.

Now take the number 1, (1-1)! + 1 = 0! + 1 = 2.

2 is divisible by 1, so why isn't 1 prime?

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