vigintillion

noun

vi·​gin·​til·​lion ˌvī-ˌjin-ˈtil-yən 

often attributive

US : a number equal to 1 followed by 63 zeros see Table of Numbers

also, British : a number equal to 1 followed by 120 zeros see Table of Numbers

Word History

Etymology

Latin viginti twenty + English -illion (as in million) — more at vigesimal

First Known Use

1857, in the meaning defined above