I dunno exactly, but my brother's girlfriend's father's boss's secretary's sister's next-door neighbors' priest's cousin's union shop steward's uncle's Knights Of Columbus club Sergeant-of-Arms's nephew's best friend did it real cheap for me once.
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.