3,991 is an odd composite number composed of two prime numbers multiplied together.

What does the number 3991 look like?

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

3991 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 3991:

13 × 307

See below for interesting mathematical facts about the number 3991 from the Numbermatics database.

Names of 3991

  • Cardinal: 3991 can be written as Three thousand, nine hundred ninety-one.

Scientific notation

  • Scientific notation: 3.991 × 103

Factors of 3991

  • Number of distinct prime factors ω(n): 2
  • Total number of prime factors Ω(n): 2
  • Sum of prime factors: 320

Divisors of 3991

  • Number of divisors d(n): 4
  • Complete list of divisors:
  • Sum of all divisors σ(n): 4312
  • Sum of proper divisors (its aliquot sum) s(n): 321
  • 3991 is a deficient number, because the sum of its proper divisors (321) is less than itself. Its deficiency is 3670

Bases of 3991

  • Binary: 1111100101112
  • Hexadecimal: 0xF97
  • Base-36: 32V

Squares and roots of 3991

  • 3991 squared (39912) is 15928081
  • 3991 cubed (39913) is 63568971271
  • The square root of 3991 is 63.1743618885
  • The cube root of 3991 is 15.8620960711

Scales and comparisons

How big is 3991?
  • 3,991 seconds is equal to 1 hour, 6 minutes, 31 seconds.
  • To count from 1 to 3,991 would take you about six 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 3991 cubic inches would be around 1.3 feet tall.

Recreational maths with 3991

  • 3991 backwards is 1993
  • The number of decimal digits it has is: 4
  • The sum of 3991's digits is 22
  • More coming soon!

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The information we have on file for 3991 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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