Three: one to write the light bulb removal program, one to write the light bulb insertion program, and one to act as a light bulb administrator to make sure nobody else tries to change the light bulb at the same time.
Two: One to screw it in and one to observe how the light bulb itself symbolizes a single incandescent beacon of subjective reality in a netherworld of endless absurdity reaching out toward a maudlin cosmos of nothingness.