qua·dril·lion /kwɑˈdrɪljən/
百萬之四次方
Quad·ril·lion n. According to the French notation, which is followed also upon the Continent and in the United States, a unit with fifteen ciphers annexed; according to the English notation, the number produced by involving a million to the fourth power, or the number represented by a unit with twenty-four ciphers annexed. See the Note under Numeration.
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quadrillion
n 1: the number that is represented as a one followed by 24
zeros; "in England they call a septillion a quadrillion"
2: the number that is represented as a one followed by 15 zeros