The guy on the end of the line can receive a forward pass.
So, if the snapper is at the end of that side of the line, he can catch the football.
But numbers? Thought centers needed to be 50’s so they were identified, regardless of line position. Ends are 80’s and 90’s, blockers are 60’s and 70’s for the same reason. So you can tell who is eligible to receive.
Offensive line numbers are typically from 50 to 79 regardless of position. If one of these guys lines up as an eligible receiver (on the end of the line) and are going to participate in something other than line play, they have to report to the referee.