48

 48 is the atomic number of Cadmium (a metal), and the international telephone country code for Poland. 

It is a highly favorable number in Chinese Numerology.

It's the number of US states in the contingent "lower 48."

There are 48 preludes and fugues in Bach's "The Well-Tempered Clavier." (No, I didn't remember this from Music History from over 25 years ago, I Googled it like a normal person.)

On a musical metronome, it falls under Lento (slow).

And...48 is my age today.