7 * 11 * 13 = 1001

So, any 3 digit number which is "doubled" on itself... for example 413 - > 413413 is
essentially multiplied by 1001 - > 413 * 1001 = 413413

which is 413 * 7 * 11 * 13 = 413413 = 413 * 1001.

Tommy

>OK, more than a puzzle, this is an interesting mathematical oddity. You may want to explain how come, though.
>
>

Take any three-digit number (e.g.: 413).
>

Repeat the digits once more (e.g.: 413413).
>

Divide the resulting number by 7 (e.g.: 59059).
>

Divide the result by 11 (e.g.: 5369).
>

Divide the result by 13 (e.g.: 413).
>
>Oddity number one: dividing succesively by 7, 11, and 13, results in an integer (or, in other words, no remainder), no matter with what number you start.
>
>Oddity number two: you always get your original number back..
>
>Hilmar.

Tommy Tillman A+ NetWork+ MCP