An exabyte is 2 to the 60th power, or 1,152,921,504,606,846,976 bytes.
It can be estimated as 10 to the 18th power, or 1,000,000,000,000,000,000 bytes. An exabyte is 1,024 petabytes and precedes the zettabyte unit of measurement. While a 64-bit processor can theoretically use 16 exabytes of address space, exabytes are so large, the units are rarely used in a practical context. For example, it is estimated that all the printed material in the world only takes up about five exabytes.
For a list of all the different units of measurements, view this Help Center article.