About the Number 18 (eighteen)

This BAB was created after MathBabbler wrote a BAB about university presidents wanting to lower the drinking age to 18 and discovered he didn't have a number BAB for the number 18.

   MathBabbler Number Analyst (MBNA) output:
   =========================================
   18 is a natural, whole, integer
   18 is even
   18 proper divisors are: 1,2,3,6,9
   18 is abundant (sum of divisors is 21)
   18 is unhappy
   18 is a Harshad number
   18 is not prime
   18 is undulating
   18 has the prime factors: 2*3*3
   18 in octal is 022
   18 in hexadecimal is 0x12
   18 in binary is 10010 (is evil)
   18 nearest square numbers: -2...7 (16 [4]...25 [5])
   sqrt(18) = 4.24264
   ln(18) = 2.89037
   log(18) = 1.25527
   18 reciprocal is .05555555555555555555555555555555
   18 is 5.72958 Pi years
   18 is 0 score and 18 years

18 written as a Roman numeral is XVIII.

Wikipedia tidbits about the number 18...

• "18, aside from 0, is the only number that equals twice the sum of its decimal digits"
• 18 is a semiperfect (pseudoperfect) number (i.e. it is equal to the sum of all or some of its proper divisors) [Note: The MBNA does not check for semiperfect numbers.]

The song title "Hangar 18" by Megadeth was added to /gdt/math/songs/index.html#hangar18'>Songs With Numbers In Their Titles as a result of BABbling about the number 18.

Update::2008.12.05

This nBAB was updated on 5 December 2008, which was the 75th anniversary of the ratification of the 21st Amendment. The 21st Amendment repealed the 18th Amendment (Prohibition).

Creator: Gerald Thurman [gthurman@gmail.com]
Created: 20 August 2008