391

391 is an odd composite number composed of two prime numbers multiplied together.

What does the number 391 look like?

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

391 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 391:

17 × 23

See below for interesting mathematical facts about the number 391 from the Numbermatics database.


Names of 391

  • Cardinal: 391 can be written as Three hundred ninety-one.

Scientific notation

  • Scientific notation: 3.91 × 102

Factors of 391

  • Number of distinct prime factors ω(n): 2
  • Total number of prime factors Ω(n): 2
  • Sum of prime factors: 40

Divisors of 391

  • Number of divisors d(n): 4
  • Complete list of divisors:
  • Sum of all divisors σ(n): 432
  • Sum of proper divisors (its aliquot sum) s(n): 41
  • 391 is a deficient number, because the sum of its proper divisors (41) is less than itself. Its deficiency is 350

Bases of 391

  • Binary: 1100001112
  • Hexadecimal: 0x187
  • Base-36: AV

Squares and roots of 391

  • 391 squared (3912) is 152881
  • 391 cubed (3913) is 59776471
  • The square root of 391 is 19.7737199333
  • The cube root of 391 is 7.3123828115

Scales and comparisons

How big is 391?
  • 391 seconds is equal to 6 minutes, 31 seconds.
  • To count from 1 to 391 would take you about 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 391 cubic inches would be around 0.6 feet tall.

Recreational maths with 391

  • 391 backwards is 193
  • The number of decimal digits it has is: 3
  • The sum of 391's digits is 13
  • More coming soon!

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The information we have on file for 391 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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