821 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 821 look like?

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

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

Prime factorization of 821:


See below for interesting mathematical facts about the number 821 from the Numbermatics database.

Names of 821

  • Cardinal: 821 can be written as Eight hundred twenty-one.

Scientific notation

  • Scientific notation: 8.21 × 102

Factors of 821

  • Number of distinct prime factors ω(n): 1
  • Total number of prime factors Ω(n): 1
  • Sum of prime factors: 821

Divisors of 821

  • Number of divisors d(n): 2
  • Complete list of divisors:
    1 821
  • Sum of all divisors σ(n): 822
  • Sum of proper divisors (its aliquot sum) s(n): 1
  • 821 is a deficient number, because the sum of its proper divisors (1) is less than itself. Its deficiency is 820

Bases of 821

  • Binary: 11001101012
  • Hexadecimal: 0x335
  • Base-36: MT

Squares and roots of 821

  • 821 squared (8212) is 674041
  • 821 cubed (8213) is 553387661
  • The square root of 821 is 28.6530975637
  • The cube root of 821 is 9.3637049155

Scales and comparisons

How big is 821?
  • 821 seconds is equal to 13 minutes, 41 seconds.
  • To count from 1 to 821 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 821 cubic inches would be around 0.8 feet tall.

Recreational maths with 821

  • 821 backwards is 128
  • 821 is a twin prime! Its twin is 823
  • The number of decimal digits it has is: 3
  • The sum of 821's digits is 11
  • More coming soon!

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"Number 821 - Facts about the integer". Numbermatics.com. 2024. Web. 17 July 2024.

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Numbermatics. (2024). Number 821 - Facts about the integer. Retrieved 17 July 2024, from https://numbermatics.com/n/821/

Chicago style:
Numbermatics. 2024. "Number 821 - Facts about the integer". https://numbermatics.com/n/821/

The information we have on file for 821 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 821, math, Factors of 821, curriculum, school, college, exams, university, Prime factorization of 821, STEM, science, technology, engineering, physics, economics, calculator, eight hundred twenty-one.

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