81
81 is an odd composite number. It is composed of a single prime number multiplied by itself three times.
81 is an odd composite number. It is composed of one distinct prime number multiplied by itself three times. It has a total of five divisors.
Prime factorization of 81:
34
(3 × 3 × 3 × 3)See below for interesting mathematical facts about the number 81 from the Numbermatics database.
Names of 81
- Cardinal: 81 can be written as Eighty-one.
Scientific notation
- Scientific notation: 8.1 × 101
Factors of 81
Divisors of 81
Bases of 81
- Binary: 10100012
- Hexadecimal: 0x51
- Base-36: 29
Squares and roots of 81
Scales and comparisons
How big is 81?- 81 seconds is equal to 1 minute, 21 seconds.
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To count from 1 to 81 would take you about forty seconds.
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 81 cubic inches would be around 0.4 feet tall.
Recreational maths with 81
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The information we have on file for 81 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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