Googolplex
A googol is 10 to the 100th power (that is 1 followed by 100 zeros).
A googol is bigger than the range of elementary particles in the universe, which amount to only 10 to the 80th power.
The term was invented by Milton Sirotta, the 9-year nephew of mathematician Edward Kasner, who had asked his nephew what he thought such a massive number should be called.