N641K is taken. It's currently assigned to a Kenneth Owings ZENITH STOL CH 750.
See the full aircraft record →A tail number only frees up if the owner deregisters the aircraft or moves it to a different N-number — and even then the FAA holds it before releasing it to the public.
N641K has been worn before. Past registrations from FAA deregistration records:
Tails one nudge away from N641K that aren't assigned or reserved: