721

Names of 721

• Cardinal: 721 can be written as Seven hundred twenty-one.

Scientific notation

• Scientific notation: 7.21 × 10²

Factors of 721

• Number of distinct prime factors ω(n): 2
• Total number of prime factors Ω(n): 2
• Sum of prime factors: 110

Divisors of 721

• Number of divisors d(n): 4
• Complete list of divisors:
  1 7 103 721
• Sum of all divisors σ(n): 832
• Sum of proper divisors (its aliquot sum) s(n): 111
• 721 is a deficient number, because the sum of its proper divisors (111) is less than itself. Its deficiency is 610

Bases of 721

• Binary: 1011010001₂
• Hexadecimal: 0x2D1
• Base-36: K1

Squares and roots of 721

• 721 squared (721²) is 519841
• 721 cubed (721³) is 374805361
• The square root of 721 is 26.8514431639
• The cube root of 721 is 8.9669570223

Scales and comparisons

• 721 seconds is equal to 12 minutes, 1 second.
• To count from 1 to 721 would take you about six 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 721 cubic inches would be around 0.7 feet tall.

Recreational maths with 721

• 721 backwards is 127
• The number of decimal digits it has is: 3
• The sum of 721's digits is 10
• More coming soon!