What are the most number of propellors that a rotorcraft has been flown with?
This guy is actually flying with 76 rotors.

But I might argue that your "more rotors is faster" idea may be flawed, smaller propellers are less efficient (because the further from the center you are, the faster the blade is moving, if I'm not mistaken), so the trade may be fewer, more efficient, propellers for a larger number of less efficient ones.