991

Names of 991

• Cardinal: 991 can be written as Nine hundred ninety-one.

Scientific notation

• Scientific notation: 9.91 × 10²

Factors of 991

• Number of distinct prime factors ω(n): 1
• Total number of prime factors Ω(n): 1
• Sum of prime factors: 991

Divisors of 991

• Number of divisors d(n): 2
• Complete list of divisors:
  1 991
• Sum of all divisors σ(n): 992
• Sum of proper divisors (its aliquot sum) s(n): 1
• 991 is a deficient number, because the sum of its proper divisors (1) is less than itself. Its deficiency is 990

Bases of 991

• Binary: 1111011111₂
• Hexadecimal: 0x3DF
• Base-36: RJ

Squares and roots of 991

• 991 squared (991²) is 982081
• 991 cubed (991³) is 973242271
• The square root of 991 is 31.4801524773
• The cube root of 991 is 9.9699095473

Scales and comparisons

• 991 seconds is equal to 16 minutes, 31 seconds.
• To count from 1 to 991 would take you about eight minutes.

  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 991 cubic inches would be around 0.8 feet tall.

Recreational maths with 991

• 991 backwards is 199
• The number of decimal digits it has is: 3
• The sum of 991's digits is 19
• More coming soon!