Quintillion

A quintillion is equal to 1018 in short scale Chuquet nomenclature. In the long scale, this number is called trillion. In the long scale it is the fifth power of a million and in the short scale the fifth power of a thousand starting with a million. This number is also called hexillion in Russ Rowlett's Greek-based naming system. Aarex Tiaokhiao calls this number hetillion. He also gave name ocdoocol and 18-noogol, referring to the short scale value of this number equating to s(10,18) in Strong array notation.

In the Indian counting system, it is called ten thousand crore crore or ten shankh, although both terms are infrequently used in common parlance. The quintillion is commonly-known but less so than a trillion, and some prefer to use million trillion or billion billion instead.

Etymology
The name is derived from the Latin prefix quinti-, meaning 5, and the suffix -illion.

Examples

 * Based on Jeremy Harper's 89-day-long count to a million, we can estimate that it would take more than 243,000,000,000 years to count to a quintillion (about 17 times the age of the universe), assuming sixteen hours are allocated for counting every day.
 * The SI prefix for this number is exa-.