Fermat's theorem

         Fermat's small theorem is one of the four theorems of elementary number theory （ Wilson's theorem , Euler theorem （ Euler's theorem in number theory ）, Chinese remainder theorem ( also called Sun Tzu's Theorem ）, Fermat's small Theorem ） One of , stay Elementary number theory Has a very wide range and important applications .

         Fermat's small Theorem (Fermat's little theorem)： If p It's a Prime number , and Integers a No p Multiple , Then there are

a^（p-1）≡1（mod p）.        

         explain ：

                 One . ≡   For the identity .

                 Two .  a ^（p-1）mod p ≡ 1 mod p = 1