90

Names of 90

• Cardinal: 90 can be written as Ninety.

Scientific notation

• Scientific notation: 9 × 10¹

Factors of 90

• Number of distinct prime factors ω(n): 3
• Total number of prime factors Ω(n): 4
• Sum of prime factors: 10

Divisors of 90

• Number of divisors d(n): 12
• Complete list of divisors:
  1 2 3 5 6 9 10 15 18 30 45 90
• Sum of all divisors σ(n): 234
• Sum of proper divisors (its aliquot sum) s(n): 144
• 90 is an abundant number, because the sum of its proper divisors (144) is greater than itself. Its abundance is 54

Bases of 90

• Binary: 1011010₂
• Hexadecimal: 0x5A
• Base-36: 2I

Squares and roots of 90

• 90 squared (90²) is 8100
• 90 cubed (90³) is 729000
• The square root of 90 is 9.4868329807
• The cube root of 90 is 4.4814047465

Scales and comparisons

• 90 seconds is equal to 1 minute, 30 seconds.
• To count from 1 to 90 would take you about forty-five 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. (We do not count involuntary pauses, bathroom breaks or the necessity of sleep in our calculation!)

• A cube with a volume of 90 cubic inches would be around 0.4 feet tall.

Recreational maths with 90

• 90 backwards is 09
• 90 is a Harshad number.
• The number of decimal digits it has is: 2
• The sum of 90's digits is 9
• More coming soon!