While creating a collection of square numbers, MathBabbler was surprised to learn he didn't have a nBAB for the number

`.`

400MathBabbler Number Analyst (MBNA) output: ========================================= 400 is a natural, whole, integer 400 is even 400 proper divisors are: 1,2,4,5,8,10,16,20,25,40,50,80,100,200, 400 is abundant (sum of divisors is 561) 400 is unhappy 400 is a Harshad number 400 is not prime 400 has the prime factors: 2*2*2*2*5*5 400 sum prime factors: 18 400 in octal is 0620 400 in hexadecimal is 0x190 400 in binary is 110010000 (is odious) 400 is a square number sqrt(400) = 20 ln(400) = 5.99146 log(400) = 2.60206 400 is 20^2 400 reciprocal is .00250000000000000000000000000000 400! is 6.40345e+868 400 is 127.324 Pi years 400 is 20 scoreyears 400 written as a Roman numeral is CD## Update::2009.08.25

On 25 August 2009, Google morphed its logo to celebrate the 400th anniversary of Italian astronomer Galilei Galileo's demonstration of his telescope.

Between the time this nBAB was created (10 April 2009) and the time of this update, the

basenprogram was written and it produced the following output.

`in base-16 is 1024 (i.e. 2^10).`

400

`in base-15 is square number 900.`

400

`in base-8 is 256 (i.e. 2^8).`

400

`in base-7 is square number 196 (i.e. 14^2).`

400

`in base-6 is square number 144 (i.e. 12^2).`

400

`in base-5 is square number 100 (i.e. 10^2).`

400## Update::2009.12.15

MathBabbler posted his

`th tweet on 15 December 2009. MathBabbler has been tweeting at a rate of almost 2.1 tweets per day since posting his first tweet on 8 June 2009.`

400Between the date this nBAB was last updated (25 August 2009) and the date of this update, the

logsprogram was written and it reported that

log_{9}(400)`(2.72683)`

truncated to two-decimal digits equalse`(2.7182818284590)`

rounded to the nearest hundredth.MathBABs.us::Number Basic Arithmetic Bits (BABs) Homepage

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

**Created:** 10 April 2009 (posted 13 May 2009)

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