1,000,001: One to change the bulb and 1,000,000 to rebuild civilization to the point where they need light bulbs again.
or
Two, one to call the electrician, and one to mix the drinks.
or
Two: One to screw you out of a fee, and the other to send you to a store where they ran out of bulbs weeks ago.
or
Two — one to screw it most of the way in and the other to give it a surprise twist at the end.
or