9,991 is an odd composite number composed of two prime numbers multiplied together.

What does the number 9991 look like?

This visualization shows the relationship between its 2 prime factors (large circles) and 4 divisors.

9991 is an odd composite number. It is composed of two distinct prime numbers multiplied together. It has a total of four divisors.

Prime factorization of 9991:

97 × 103

See below for interesting mathematical facts about the number 9991 from the Numbermatics database.

Names of 9991

  • Cardinal: 9991 can be written as Nine thousand, nine hundred ninety-one.

Scientific notation

  • Scientific notation: 9.991 × 103

Factors of 9991

  • Number of distinct prime factors ω(n): 2
  • Total number of prime factors Ω(n): 2
  • Sum of prime factors: 200

Divisors of 9991

  • Number of divisors d(n): 4
  • Complete list of divisors:
  • Sum of all divisors σ(n): 10192
  • Sum of proper divisors (its aliquot sum) s(n): 201
  • 9991 is a deficient number, because the sum of its proper divisors (201) is less than itself. Its deficiency is 9790

Bases of 9991

  • Binary: 100111000001112
  • Hexadecimal: 0x2707
  • Base-36: 7PJ

Squares and roots of 9991

  • 9991 squared (99912) is 99820081
  • 9991 cubed (99913) is 997302429271
  • The square root of 9991 is 99.9549898705
  • The cube root of 9991 is 21.5378816563

Scales and comparisons

How big is 9991?
  • 9,991 seconds is equal to 2 hours, 46 minutes, 31 seconds.
  • To count from 1 to 9,991 would take you about two hours.

    This is a very rough estimate, based on a speaking rate of half a second every third order of magnitude. If you speak quickly, you could probably say any randomly-chosen number between one and a thousand in around half a second. Very big numbers obviously take longer to say, so we add half a second for every extra x1000. (We do not count involuntary pauses, bathroom breaks or the necessity of sleep in our calculation!)

  • A cube with a volume of 9991 cubic inches would be around 1.8 feet tall.

Recreational maths with 9991

  • 9991 backwards is 1999
  • The number of decimal digits it has is: 4
  • The sum of 9991's digits is 28
  • More coming soon!

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"Number 9991 - Facts about the integer". Numbermatics.com. 2022. Web. 9 August 2022.

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Numbermatics. (2022). Number 9991 - Facts about the integer. Retrieved 9 August 2022, from https://numbermatics.com/n/9991/

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The information we have on file for 9991 includes mathematical data and numerical statistics calculated using standard algorithms and methods. We are adding more all the time. If there are any features you would like to see, please contact us. Information provided for educational use, intellectual curiosity and fun!

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