How many football players and officials are in an NFL football game at once?

22 players (11 offense/11 defense) 5 officials (1 umpire, 1 line judge, 1 back judge, 1 side judge, 1 replay official up in the booth)

There are SEVEN officials on the field:

Referee

Head Linesman

Line Judge

Umpire

Side Judge

Field Judge

Back Judge