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Let $p,q$ be distinct primes, and let $\phi$ denote the Euler phi function. Which of the following statements is NOT true?

$\phi(pq)=\phi(p)\phi(q)$

$\phi(p^2q^3)=\phi(p^2)\phi(q^3)$

$\phi(p^4)=p^4-p^3$

$\phi(q^3)=\phi(q^2)\phi(q)$