Mathematical Black Hole

A mathematical black hole is, defined non mathematically, any number to which other elements (usually numbers) are drawn by some stated process. Though the number itself is the star of the show, the real trick is in finding interesting processes which make this "star".

Following is one example of the Mathemagical Black Hole by Martin Gardner. Take any whole number and write out its numeral in English, such as FIVE for the usual 5. Count the number of characters in the spelling. In this case, it is 4 — or FOUR. Number of characters in the spelling is 4. Repeat with 4 to get 4 again. So here the number 4 is the mathemagical black hole.

Just to prove it is not a lie, Another example lets take the number 155.
ONE HUNDRED FIFTY FIVE : Number of characters = 19
NINETEEN : Number of characters = 8
EIGHT : Number of characters = 5
FIVE : Number of characters = 4

And we repeat from here. Interesting!