645

Names of 645

• Cardinal: 645 can be written as Six hundred forty-five.

Scientific notation

• Scientific notation: 6.45 × 10²

Factors of 645

• Number of distinct prime factors ω(n): 3
• Total number of prime factors Ω(n): 3
• Sum of prime factors: 51

Divisors of 645

• Number of divisors d(n): 8
• Complete list of divisors:
  1 3 5 15 43 129 215 645
• Sum of all divisors σ(n): 1056
• Sum of proper divisors (its aliquot sum) s(n): 411
• 645 is a deficient number, because the sum of its proper divisors (411) is less than itself. Its deficiency is 234

Bases of 645

• Binary: 1010000101₂
• Hexadecimal: 0x285
• Base-36: HX

Squares and roots of 645

• 645 squared (645²) is 416025
• 645 cubed (645³) is 268336125
• The square root of 645 is 25.3968501985
• The cube root of 645 is 8.6401225977

Scales and comparisons

• 645 seconds is equal to 10 minutes, 45 seconds.
• To count from 1 to 645 would take you about five 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 645 cubic inches would be around 0.7 feet tall.

Recreational maths with 645

• 645 backwards is 546
• 645 is a Harshad number.
• The number of decimal digits it has is: 3
• The sum of 645's digits is 15
• More coming soon!