Which Russian mathmatician contributed to number theory, Grigori Perelman or Ivan Fesenko?
Grigori Perelman:  He made a contribution to Riemannian geometry and geometric topology. Ivan Fesenko: Ivan Fesenko (Russian: Иван Борисович Фесенко ; born 1962) is a mathematician working in number theory and other areas of modern mathematics.
i don't know