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I have a homework to hand in and they asked this question. I don't know if I'm supposed to count 1 as a prime to that number or not.

In my case $p=3947$, so I count 3945 numbers fitting that criteria since $p$ is prime.

Is this correct ?

Thanks.

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    $p=3947$ is prime. Therefore the answer is $\phi(p)=p-1=3946$.2012-11-15

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The correct terminology is 'co-prime' with p. And there's a known formula for it. Euler's totient. look at http://en.wikipedia.org/wiki/Euler_totient_function.

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    If you take the average of your 2 answers then you are correct!2012-11-15