A yottabyte is 2 to the 80th power, or 1,208,925,819,614,629,174,706,176 bytes.
It can be estimated as 10 to the 24th power, or 1,000,000,000,000,000,000,000,000 bytes. The yottabyte is the largest unit of measurement for computer data, consisting of 1,024 zettabytes.
Fortunately for those of us finite beings, yottabytes are not used very often. The prefix "Yotta" comes from "Iota," which is the ninth letter of the Greek alphabet. However, it seems more fitting that "yotta" refers to a "lotta" bytes.
Abbreviation: YB