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Which of the following statement(s) is(are) true?

• If $n$ is odd prime number then $2^{n-1} \text{ mod } n =1$
• If $2^{n-1} \text{ mod } n =1$ for a number $n$ then $n$ is prime
| 149 views

By taking any example we can prove it

by Veteran (119k points)
+1
@srestha,by taking any example,we will get 1 but how to make sure that it is always true.?
0
See when u get a question like this question

just take as many as value and check.

No one could check infinite times
n is odd prime number take n=3 then 2^(3-1)mod 3=2^2mod3=1

take n=7  then 2^(7-1)mod7=2^6mod7=64mod7=1 where 7 is prime.
by Active (4.1k points)

+1 vote