1991

1,991 is an odd composite number composed of two prime numbers multiplied together.

What does the number 1991 look like?

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

1991 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 1991:

11 × 181

See below for interesting mathematical facts about the number 1991 from the Numbermatics database.


Names of 1991

  • Cardinal: 1991 can be written as One thousand, nine hundred ninety-one.

Scientific notation

  • Scientific notation: 1.991 × 103

Factors of 1991

  • Number of distinct prime factors ω(n): 2
  • Total number of prime factors Ω(n): 2
  • Sum of prime factors: 192

Divisors of 1991

  • Number of divisors d(n): 4
  • Complete list of divisors:
  • Sum of all divisors σ(n): 2184
  • Sum of proper divisors (its aliquot sum) s(n): 193
  • 1991 is a deficient number, because the sum of its proper divisors (193) is less than itself. Its deficiency is 1798

Bases of 1991

  • Binary: 111110001112
  • Hexadecimal: 0x7C7
  • Base-36: 1JB

Squares and roots of 1991

  • 1991 squared (19912) is 3964081
  • 1991 cubed (19913) is 7892485271
  • The square root of 1991 is 44.6206230347
  • The cube root of 1991 is 12.5802832639

Scales and comparisons

How big is 1991?
  • 1,991 seconds is equal to 33 minutes, 11 seconds.
  • To count from 1 to 1,991 would take you about thirty-three minutes.

    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 1991 cubic inches would be around 1 feet tall.

Recreational maths with 1991

  • 1991 is the same when its digits are reversed! That makes it a palindromic number.
  • The number of decimal digits it has is: 4
  • The sum of 1991's digits is 20
  • More coming soon!

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"Number 1991 - Facts about the integer". Numbermatics.com. 2020. Web. 20 October 2020.

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Numbermatics. (2020). Number 1991 - Facts about the integer. Retrieved 20 October 2020, from https://numbermatics.com/n/1991/

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The information we have on file for 1991 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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