Seven. One to install the new bulb and six to figure out what to do with the old one for the next 10,000 years.
or
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.
or
Five. One to change the bulb and eleven to say they could do it faster.
or