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

`written as a Roman numeral is`

18`.`

XVIIIWikipedia tidbits about the number

`...`

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.]`

18The song title "Hangar

`" 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`.`

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 The 21st Amendment repealed the

`th Amendment (Prohibition).`

18

**Creator:** Gerald Thurman
[gthurman@gmail.com]

**Created:** 20 August 2008

This work is licensed under a Creative Commons Attribution 3.0 United States License.