How is it possible to find the shortest possible rotation period of a pulsar from a mass and a radius?
One simple method is to consider a particle of the star at the surface on the equator, this particle will feel two principal forces: a centrifugal force, $F_c$ generally acting to pull the particle off the surface and a gravitational $F_g$ (and strong nuclear?) force holding the particle to the surface.
If $F_c$ > $F_g$ then the particle will tend to leave the surface, if not then the particle will stay put.
As I suspect this is a homework question I'll leave the detailed mathematics out of it for now!