Twenty. One to hold the bulb, two to turn the ladder, and 17 to be on the guest list.
or
Two-lips!
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None, but it takes at least one to sit and pray for the old one to go back on.
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Because all his other wives support Hillary.
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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