21981

Names of 21981

• Cardinal: 21981 can be written as Twenty-one thousand, nine hundred eighty-one.

Scientific notation

• Scientific notation: 2.1981 × 10⁴

Factors of 21981

• Number of distinct prime factors ω(n): 3
• Total number of prime factors Ω(n): 3
• Sum of prime factors: 451

Divisors of 21981

• Number of divisors d(n): 8
• Complete list of divisors:
  1 3 17 51 431 1293 7327 21981
• Sum of all divisors σ(n): 31104
• Sum of proper divisors (its aliquot sum) s(n): 9123
• 21981 is a deficient number, because the sum of its proper divisors (9123) is less than itself. Its deficiency is 12858

Bases of 21981

• Binary: 101010111011101₂
• Hexadecimal: 0x55DD
• Base-36: GYL

Squares and roots of 21981

• 21981 squared (21981²) is 483164361
• 21981 cubed (21981³) is 10620435819141
• The square root of 21981 is 148.2599069203
• The cube root of 21981 is 28.0123245065

Scales and comparisons

• 21,981 seconds is equal to 6 hours, 6 minutes, 21 seconds.
• To count from 1 to 21,981 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 21981 cubic inches would be around 2.3 feet tall.

Recreational maths with 21981

• 21981 backwards is 18912
• The number of decimal digits it has is: 5
• The sum of 21981's digits is 21
• More coming soon!