>>13383132a. You'd want to use the relativistic rocket equation once you get up to those sorts of speeds, but...
b. Your units are confused. You're comparing the speed of light in km / s to delta-V you've computed in m / s (but which you've written down as unitless, which doesn't help you spot this error), so you're off by a factor of 1000, and you don't need to bother with relativity.
