Definition

1. Noun:
   • The cardinal number equal to 10²⁴ (1 followed by 24 zeros): A very large number used primarily in contexts like mathematics, astronomy, and finance, especially in systems using the long scale numbering convention.

Usage Examples

• Noun:
  • The estimated number of stars in the observable universe is in the septillions.
  • In the long scale system, a septillion is equivalent to a quadrillion in the short scale system used in the United States.

Advanced Usage

• Scientific Notation: Often expressed as 10²⁴ for clarity in scientific and technical writing.
  • The mass of the Earth is approximately 6 septillion kilograms (6 × 10²⁴ kg).
• Comparative Context: Used to illustrate immense quantities.
  • The national debt reached a figure in the septillions of the local currency.

Variants and Related Words

• Septillionth (ordinal number & noun): Constituting number septillion in a sequence; one of septillion equal parts.
  • He finished in septillionth place in the massive online competition.
  • A septillionth of a gram is an almost immeasurably small unit.

Synonyms

• 10²⁴: The expression in scientific notation.
• (In long scale): Quadrillion (This is the short scale U.S. equivalent; the synonym is context-dependent on the numbering system used.)

Notes on Numbering Scales

• Long Scale: Used in most European countries and many others worldwide. In this system, each new term greater than a million is 1,000,000 times the previous term (a billion is 10¹², a trillion is 10¹⁸, a septillion is 10²⁴).
• Short Scale: Used primarily in the United States and modern British English. In this system, each new term greater than a thousand is 1,000 times the previous term (a billion is 10⁹, a trillion is 10¹², a quadrillion is 10¹⁵, and the number 10²⁴ is called a septillion).

Noun

1. the number that is represented as a one followed by 24 zeros