How To Tell If He Blocked My Number?

Anyone know how to tell if someone has blocked your number as opposed to just ignored your text/call? I texted my ex and he hasn't replied. It's been a little over 24 hours. We didn't end our replationship as friends but I really didn't feel we ended as enemies either. Just wanted to ask him for work related advice. I haven't contacted him since we broke up 2 months ago.