9 is an odd composite number. It is composed of a single prime number multiplied by itself.

9 is an odd composite number. It has a total of three divisors.

Prime factorization of 9:


(3 × 3)

See below for interesting mathematical facts about the number 9 from the Numbermatics database.

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Names Factors Divisors Scales Roots Fun

Names of 9

  • Cardinal: 9 can be written as Nine.

Scientific notation

  • Scientific notation: 9 × 100

Factors of 9

  • Number of distinct prime factors ω(n): 1
  • Total number of prime factors Ω(n): 2
  • Sum of prime factors: 3

Divisors of 9

  • Number of divisors d(n): 3
  • Complete list of divisors:
    1 3 9
  • Sum of all divisors σ(n): 13
  • Sum of proper divisors (its aliquot sum) s(n): 4
  • 9 is a deficient number, because the sum of its proper divisors (4) is less than itself. Its deficiency is 5

Bases of 9

  • Binary: 1001 2
  • Hexadecimal: 0x9

Squares and roots of 9

  • 9 squared (92) is 81
  • 9 cubed (93) is 729
  • 9 is a perfect square number. Its square root is 3
  • The cube root of 9 is 2.0800838231

Scales and comparisons

How big is 9?
  • To count from 1 to 9 would take you about four 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.

    Note: we do not count involuntary pauses, bathroom breaks or the necessity of sleep in our calculation!

  • A cube with a volume of 9 cubic inches would be around 0.2 feet tall.

Recreational maths with 9

  • 9 is the same when its digits are reversed! That makes it a palindromic number.
  • 9 is a Harshad number.
  • The number of decimal digits it has is: 1
  • The sum of 9's digits is 9
  • More coming soon!

The information we have on file for 9 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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