Yotta (Y) is the prefix for a septillion. In decimal notation, it is the 24-digit decimal number 1,000,000,000,000,000,000,000; in exponential notation, it is: 10exp24 or 10high24.
In the dual system, a yottabyte (YB) is equivalent to 2exp80. The next highest prefix is Bronto. It corresponds to 10exp27.
Yottabytes, a tremendously large amount of data, is mentioned in connection with the spying of communication connections by the American National Security Agency (NSA). The prefix Yotta, like all other mathematical prefixes, is defined in the Système International (SI).