I'm not really fond of practical math, but the concept of numbers & calculating value is a cognititve ability that has fascinated people since the beginning of counted time. The list in the link above names a "special" feature about each number from 0 through 9999. I'm sure the more you love math, the more special they are.
I've read a couple books on the Divine Ratio aka Phi aka 1.618... It's one of those things if you think about too much, your brain will overload.