quadrillion (n.) Look up quadrillion at Dictionary.com
1670s, from French quadrillion (16c.) from quadri- "four" (from PIE root *kwetwer- "four") + (m)illion. Compare billion. In Great Britain, the fourth power of a million (1 followed by 24 zeroes); in the U.S., the fifth power of a thousand (1 followed by 15 zeroes).