What is a googleplex?

Any numbers hound (and Rob's four-year-old son) knows that a googol is a 1 with a hundred zeroes after it (10 to the hundredth power), and a googolplex is a one with a googol zeroes after it (10 to the googolth power).

After thinking about buying The Google Legacy by Stephen E. Arnold, I now know what a Googleplex is.

A dollar sign with a 180 after it.

$180? For a PDF? Wow. Um. Thanks for the free chapter.

[Update 8/2/2006]
I see lots of people who hit this post after searching on "What is a googleplex?". To you people, I have two things to say:

1. A googol is 10 to the hundredth power:

10,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,
000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000.

A googolplex is 10 to the googolth power; I'm not going to write that number here. It's huge.
2. Don't type "what is a" into Google. It doesn't help your search. Just type "googleplex".