Quadrillion
The quadrillion is a large number which has one of two values depending on where it is used:
American usage
A quadrillion is equal to a 1 with 15 zeroes, namely:
1,000,000,000,000,000 (1015)
It is a thousand trillion and one thousandth of a quintillion. The SI prefix for this number is peta-.
European usage
A quadrillion is equal to a 1 with 24 zeroes, namely:
1,000,000,000,000,000,000,000,000 (1024)
It is a million trillion and one millionth of a quintillion, or, a thousand trilliard and one thousandth of a quadrilliard. The SI prefix for this number is yotta-.
While people in the British Isles, Australia and New Zealand traditionally employed the European usage, they have recently largely switched to the U.S. version.
See also List of numbers.
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