28 is an even composite number composed of two prime numbers multiplied together.

28 is an even composite number. It is composed of two distinct prime numbers multiplied together. It has a total of six divisors.

Prime factorization of 28:

22 × 7

(2 × 2 × 7)

See below for interesting mathematical facts about the number 28 from the Numbermatics database.

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Names Factors Divisors Scales Roots Fun

Names of 28

  • Cardinal: 28 can be written as Twenty-eight.

Scientific notation

  • Scientific notation: 2.8 × 101

Factors of 28

  • Number of distinct prime factors ω(n): 2
  • Total number of prime factors Ω(n): 3
  • Sum of prime factors: 9

Divisors of 28

  • Number of divisors d(n): 6
  • Complete list of divisors:
    1 2 4 7 14 28
  • Sum of all divisors σ(n): 56
  • Sum of proper divisors (its aliquot sum) s(n): 28
  • 28 is a perfect number. It is exactly equal to the sum of its proper divisors

Bases of 28

  • Binary: 11100 2
  • Hexadecimal: 0x1c

Squares and roots of 28

  • 28 squared (282) is 784
  • 28 cubed (283) is 21952
  • The square root of 28 is 5.2915026221
  • The cube root of 28 is 3.0365889719

Scales and comparisons

How big is 28?
  • To count from 1 to 28 would take you about fourteen 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 28 cubic inches would be around 0.3 feet tall.

Recreational maths with 28

  • 28 backwards is 82
  • The number of decimal digits it has is: 2
  • The sum of 28's digits is 10
  • More coming soon!

The information we have on file for 28 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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