Answers by visitors named: Soukayna

We have (A) : 29^(p)=-1(mod p) , so 29^(2p) = 1(mod p) Let k=ord p (29) k | 2p implies k={1, 2} since k is different from p from (A). If k=1 we get : 28 = 0(mod p) which means p € {2, 7}. If k=2 we get : 840=0(mod p) which means p € {2, 3, 5, 7}. Finally, there are 4 prime numbers.