Not an impressive number. Nothing special about it. You're still not old enough to drink. $20 won't buy a tank of gas. There's really nothing about the number that makes it stick out in any way.
Until you start talking pounds.
I've lost 20 pounds. Again, even at that point, nothing spectacular, but enough that people are beginning to notice.
So to me, 20 is a ridiculously magical number right now.