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Exercise: Compute the result of φ(15).
By applying a combination of the facts about computing the Euler totient function φ for prime numbers, powers of primes, and products of coprime numbers, we can compute the solution as follows:
φ(15)
=
φ(3) ⋅ φ(5)
=
(3 − 1) ⋅(5 − 1)
=
8