A googol is a large number equal to 
(i.e., a 1 with 100 zeros following it).
Written out explicitly,
10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000.
The term was coined in 1938 by 9-year-old Milton Sirotta, nephew of Edward Kasner (Kasner 1989, pp. 20-27; Bialik 2004). Kasner then extended the term to the larger "googolplex." It should be noted that "googol" is indeed the correct spelling of the term, so the spelling "Google" refers to the internet search engine, not one with 100 zeros.
The residues of googol (mod 
)
for 
, 2, ... are 0, 0, 1, 0, 0, 4, 4, 0,
1, 0, ... (OEIS A066298).
The integer sequence 
that counts the number of 
matrices over an alphabet of size 10 and having first few terms 10, 10000, 1000000000,
... (OEIS A076782) reaches googol at its 10th
term, and googolplex (
) at its 
term. Since 
grows exponentially, this gives an idea of how big
a googolplex is with respect to the size of googol.
