septillion

noun

sep·​til·​lion sep-ˈtil-yən 

often attributive

US : a number equal to 1 followed by 24 zeros see Table of Numbers

also, British : a number equal to 1 followed by 42 zeros see Table of Numbers

Examples of septillion in a Sentence

Recent Examples on the Web

If the average galaxy contains around 100 billion stars, that works out to roughly one septillion stars. — Kaif Shaikh, Interesting Engineering, 7 July 2026

Quantum computers calculate in fractions of a second what would have taken classical supercomputers septillions of years, enabling us to create personalized pharmaceuticals and materials with extraordinary properties. — David Awschalom, Chicago Tribune, 26 Apr. 2026

Extrapolating from the National Weather Service estimates, the likelihood of being struck six times is roughly one in 13 septillion—that’s a 13 followed by 24 zeros. — Jacob Stern, The Atlantic, 16 Mar. 2026

Willow was able to reduce errors exponentially by using more qubits and perform a standard benchmark computation in under 5 minutes that would take one of today’s fastest supercomputers 10 septillion years, the report said. — Pia Singh, CNBC, 19 Jan. 2026

Word History

Etymology

French, from Latin septem + French -illion (as in million) — more at seven

First Known Use

1690, in the meaning defined above

Rhymes for septillion

• castilian
• civilian
• cotillion
• pavilion
• postilion
• quadrillion
• reptilian
• vermilion
• vermillion
• billion
• million
• pillion

Kids Definition

septillion

noun

sep·​til·​lion sep-ˈtil-yən 

US : a number equal to 1 followed by 24 zeros see number

also, British : a number equal to 1 followed by 42 zeros see number