Question 1207613
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Answer: <font color=red>4</font>


Explanation


For any prime p, we have the following:
phi(p) = p-1


There are p-1 positive integers smaller than p that are relatively prime to p.
1, 2, 3, ..., p-2, p-1
This intuitively makes sense because all of these values are not factors of the prime p (well except for the trivial case 1)


Examples:
phi(7) = 6
phi(11) = 10


If we had some value not relatively prime to p, smaller than p, then it would mean p isn't prime.
For instance if 2 and p weren't relatively prime, then p = 2k and p is even. But at this point p is not prime.


Further Reading
<a href="https://mathworld.wolfram.com/TotientFunction.html">https://mathworld.wolfram.com/TotientFunction.html</a>
and
<a href="https://en.wikipedia.org/wiki/Euler%27s_totient_function">https://en.wikipedia.org/wiki/Euler%27s_totient_function</a>
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