21991

Names of 21991

• Cardinal: 21991 can be written as Twenty-one thousand, nine hundred ninety-one.

Scientific notation

• Scientific notation: 2.1991 × 10⁴

Factors of 21991

• Number of distinct prime factors ω(n): 1
• Total number of prime factors Ω(n): 1
• Sum of prime factors: 21991

Divisors of 21991

• Number of divisors d(n): 2
• Complete list of divisors:
  1 21991
• Sum of all divisors σ(n): 21992
• Sum of proper divisors (its aliquot sum) s(n): 1
• 21991 is a deficient number, because the sum of its proper divisors (1) is less than itself. Its deficiency is 21990

Bases of 21991

• Binary: 101010111100111₂
• Hexadecimal: 0x55E7
• Base-36: GYV

Squares and roots of 21991

• 21991 squared (21991²) is 483604081
• 21991 cubed (21991³) is 10634937345271
• The square root of 21991 is 148.2936276447
• The cube root of 21991 is 28.0165718227

Scales and comparisons

• 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

• 21991 backwards is 19912
• The number of decimal digits it has is: 5
• The sum of 21991's digits is 22
• More coming soon!