The main goal of the conference “Number Theory Days 2017” is to bring together the mathematicians specializing in number theory, in particular analytic number theory. The event will be open to all mathematicians, in particular those working in Poland in all areas of number theory. It will enable participants to present recent results in this discipline and it should stimulate future collaboration between them. The conference will be organized on the occasion of the 60th birthday of professor Jerzy Kaczorowski. The international recognition of the jubilarian in the world of mathematics and his important contributions in analytic number theory will make it possible to gather the world's top specialists in this discipline.