It would still be E = hf, same as for other particles with nonzero rest mass, such as electrons. Likewise the momentum would still be given by [itex]p = h / \lambda[/itex]. What would change would be the relationship between energy and momentum, which would be [itex]E = \sqrt{(pc)^2 + (m_0 c^2)^2}[/itex] instead of E = pc.