The very few friends close enough to ask that question either don't care or already know.
On the rare occasion a new acquaintance should ask that question I will pause, stare off into space for a few minutes, maybe move my lips like I'm mentally counting, then come back and say " I don't know for sure anymore, I'd have to count them."
Strangers or even worse, survey takers, either get no answer if I'm in a really good mood or "none of your damn business" if I'm not. I think the last time I was in a really good mood was Spring of '07.