As of 2014, the centillion is the largest lexicographically accepted number. As such, there is no larger number in any official dictionary. In the American numeral system, the centillion is the number one followed by 303 zeros, and in the European system it is one followed by 600 zeros.
Outside of official circles, there are other named numbers such as the googol and the googolplex, which were first described by American mathematician Edward Kasner in 1940. The googol is one followed by 100 zeros and is far less than a centillion. The googolplex, however, is one followed by a googol of zeros and is far in excess of a centillion.