By (5),
(6)p/k.
Hence the order of k (mod p) exists . Let us denote it by b .Then k^m
≡1(mod p) if and only if bm. Hence
(7) b /p---1
And , by (5), b/ k/ d_0, whice implies
(8) b/k.
I shall prove that
(9) b=k.
Suppose this is not so .Then , by (8), k/b is an integer greater than 1.
Hence there is a prime q such that