An upper bound for the number of smooth values of a polynomial and its applications

We prove a new upper bound for the number of smooth values of a polynomial with integer coefficients. This improves Timofeev’s previous result unless the polynomial is a product of linear polynomials with integer coefficients. As an application, we provide another proof for a result of Cassels which was used to prove that the Hurwitz zeta-function with algebraic irrational parameter has infinitely many zeros on the domain of convergence. We also apply the main result to a problem on primitive divisors of quadratic polynomials.