991 is a prime number. Like all primes greater than two, it is odd and has no factors apart from itself and one.

What does the number 991 look like?

As a prime, it is not composed of any other numbers and has no internal structure.

991 is a prime number. Like all primes (except two), it is an odd number.

Prime factorization of 991:


See below for interesting mathematical facts about the number 991 from the Numbermatics database.

Names of 991

  • Cardinal: 991 can be written as Nine hundred ninety-one.

Scientific notation

  • Scientific notation: 9.91 × 102

Factors of 991

  • Number of distinct prime factors ω(n): 1
  • Total number of prime factors Ω(n): 1
  • Sum of prime factors: 991

Divisors of 991

  • Number of divisors d(n): 2
  • Complete list of divisors:
    1 991
  • Sum of all divisors σ(n): 992
  • Sum of proper divisors (its aliquot sum) s(n): 1
  • 991 is a deficient number, because the sum of its proper divisors (1) is less than itself. Its deficiency is 990

Bases of 991

  • Binary: 11110111112
  • Hexadecimal: 0x3DF
  • Base-36: RJ

Squares and roots of 991

  • 991 squared (9912) is 982081
  • 991 cubed (9913) is 973242271
  • The square root of 991 is 31.4801524773
  • The cube root of 991 is 9.9699095473

Scales and comparisons

How big is 991?
  • 991 seconds is equal to 16 minutes, 31 seconds.
  • To count from 1 to 991 would take you about eight 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 991 cubic inches would be around 0.8 feet tall.

Recreational maths with 991

  • 991 backwards is 199
  • The number of decimal digits it has is: 3
  • The sum of 991's digits is 19
  • More coming soon!

Link to this page

HTML: To link to this page, just copy and paste the link below into your blog, web page or email.

BBCODE: To link to this page in a forum post or comment box, just copy and paste the link code below:

Cite this page

MLA style:
"Number 991 - Facts about the integer". Numbermatics.com. 2021. Web. 19 October 2021.

APA style:
Numbermatics. (2021). Number 991 - Facts about the integer. Retrieved 19 October 2021, from https://numbermatics.com/n/991/

Chicago style:
Numbermatics. 2021. "Number 991 - Facts about the integer". https://numbermatics.com/n/991/

The information we have on file for 991 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!

Keywords: Divisors of 991, math, Factors of 991, curriculum, school, college, exams, university, Prime factorization of 991, STEM, science, technology, engineering, physics, economics, calculator, nine hundred ninety-one.