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
he said "Not you again".
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Seven. One to change it and the other six to sing about how good the old one was.
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Two. One to hold the bulb and the other to rotate the planet.
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Drinking, bathing, washing, swimming, etc.
or