I want to ask someone who plays football what number stands on the back of his football shirt... What's the correct way to put it?
If you're talking about American football, I would say "What's your jersey number?" or "Oh you play football? What's your number?". I'd probably use the same terms for most sports, although I'm not a sports fan and I'm not sure that "jersey" is the best choice for all team sports.
Some other suggestions from Wikipedia are
- uniform number
- squad number
- jersey number
- shirt number
- sweater number