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Euler's totient function $\varphi(n)$ is defined as the number of integers from 1 to $n$ that are coprime to $n$. Two integers are coprime if their greatest common divisor is 1.

Conditions: $n$ is a positive integer.; The counting range is from 1 to $n$ inclusive.; Coprimality is determined by the greatest common divisor being 1.

Euler's totient function $\varphi(n)$ is defined as the number of integers from 1 to $n$ that are coprime to $n$. Two integers are coprime if their greatest common divisor is 1.

Conditions: $n$ is a positive integer.; The counting range is from 1 to $n$ inclusive.; Coprimality is determined by the greatest common divisor being 1.