In American mathematics, the number 1 followed by 303 zeros; in British mathematics, the number 1 followed by 600 zeros.
From 'centi-' (hundred, meaning the 100th power) + '-illion' (a suffix for large numbers). The word was coined in the 16th century as mathematicians created names for increasingly large numbers.
American and British mathematicians actually disagree on what a centillion is—the American version is a 10^303, while the British 'long scale' makes it 10^600—and this difference comes from two different historical systems of naming huge numbers that never standardized!
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