666 is considered to be the "number of the devil" and hence people seem to be afraid of it. Would you want to live on 666 Whatever Street? No, you probably wouldn't. But why not?
Some people take it a step further, being reluctant to live in 6 Whatever Street either.
There's also the fear of the number 13 (I believe it even had a long technical "-phobia" term) which I've never understood. Fear of 666, devil, sure. But what's wrong with 13? It's just a funny-looking prime number.
In Chinese culture, there's a fear of the number 4, because it is pronounced similarly to the word "die" (as in death). This is similar to the fear of 6 or 666.
Aren't these superstitions a huge practicality problem? Sometimes, it's taken too far. Some buildings don't have a 13th floor (or 6th or 4th) because of these superstitions. Why do we continue to fear these numbers? Is it because of some sort of social stigma, like the sleaziness that surrounds the number 69?
On a related note - we have numbers we seem to see as "good" as well, like the number 7 (supposedly lucky) and even 42 (the meaning of life, the universe, and everything according to "The Hitchhicker's Guide To The Galaxy" by Douglas Adams).


