A number of what? ----- ADDED AFTER CLARIFICATION ------------- "The Largest Number? I frequently get mails from people that challenge the somewhat popular opinion that Googolplex is the largest number by sending me proposals of even bigger numbers. Of course, that "popular opinion" is nonsense: there is no largest number. For example, 2*Googolplex is larger than Googolplex. Its stand-out feature is that it remains the largest number with a common name. With mathematical notation, it's no problem at all to design much larger numbers and to give name to them. By analogy, you could define Googolplexplex to be 10 to the power of Googolplex. Or you could give a name to 10^9^8^7^6^5^4^3^2^1^0 (as an exercise, the proof that this number, using a right-associative exponentiation operator, is larger than Googolplex is left to the reader). However, you will have a hard time convincing a large-enough fraction of the population of your invention so that the name becomes household. The thing about Googolplex is that it is well-enough known to be listed in dictionaries and encyclopaedias, even if only for its entertainment value. In any case, I've got you beaten. For the record, I define a Frank to be one more than the largest number you can come up with." Source and further information: http://www.fpx.de/fp/Fun/Googolplex/