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 not prime
18 is undulating
18 has the prime factors: 2*3*3
18 in octal is 022
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 The 21st Amendment repealed the `18`th Amendment (Prohibition).

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