21991 is a prime number. Like all primes (except two), it is an odd number.
Prime factorization of 21991:
See below for interesting mathematical facts about the number 21991 from the Numbermatics database.
Names of 21991
- Cardinal: 21991 can be written as Twenty-one thousand, nine hundred ninety-one.
- Scientific notation: 2.1991 × 104
Factors of 21991
Divisors of 21991
Bases of 21991
- Binary: 1010101111001112
- Hexadecimal: 0x55E7
- Base-36: GYV
Squares and roots of 21991
Scales and comparisonsHow big is 21991?
- 21,991 seconds is equal to 6 hours, 6 minutes, 31 seconds.
To count from 1 to 21,991 would take you about six hours.
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 21991 cubic inches would be around 2.3 feet tall.
Recreational maths with 21991
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
"Number 21991 - Facts about the integer". Numbermatics.com. 2022. Web. 30 June 2022.
Numbermatics. (2022). Number 21991 - Facts about the integer. Retrieved 30 June 2022, from https://numbermatics.com/n/21991/
Numbermatics. 2022. "Number 21991 - Facts about the integer". https://numbermatics.com/n/21991/
The information we have on file for 21991 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 21991, math, Factors of 21991, curriculum, school, college, exams, university, Prime factorization of 21991, STEM, science, technology, engineering, physics, economics, calculator, twenty-one thousand, nine hundred ninety-one.