Yes. 7.2.5b
At least 5 players must be numbered 50-79 and on their line of scrimmage. The rule book does not say what the players NOT on the line of scrimmage may be numbered.
#54 can be in the backfield, throw the ball or run the ball. #54 CANNOT go out for a pass, because although his POSITION is legal to go out and catch a pass, his NUMBER is invalid to catch a pass.
Technically, EVERYONE on the team may have numbers 50-79, but the team better just be running the ball or executing screen passes, because the receivers may not go downfield on a pass because even though their POSITIONS make them eligible, their NUMBERS are ineligible.