As of the 2007 season, there are 32 teams in the NFL.
There have been two teams in NFL history to have an undefeated regular season. The 2007 New England Patriots are the only team that has accomplished an undefeated regular season winning 16 games. The 1972 Miami Dolphins were the other team to have an undefeated season but the schedule in 1972 had only 14 games. That Miami team went on to win the Super Bowl that year, finishing 17-0. The 2007 Patriots lost in the Super Bowl to the New York Giants. The final record for the Patriots was 18-1.
As of the 2008 season, there are 119 Division 1-A football teams and 119 Division 1-AA football teams.
As of 2009, there are 256 games in the regular season and 11 playoff games.Each of the 32 teams plays 16 games (512 results), and in each game are two teams (256 games).
There are no more undefeated teams left in the National Football League during the 2010-2011 season
22324 undefeated teams
17 teams have gone undefeated in the regular season and of those only 1 (Indiana in 1976) has gone on to win the National Championship.
The undefeated 2009-2010: New Orleans Saints, The Indianapolis Colts, Denver Broncos, New York Giants, Minnesota Vikings.
There have been over 100 undefeated football teams in NCAA history. The most recent was the 2013 champion, Florida State (14-0).
I don't know the actual number but I'll start off the discussion with the fact that the most recent undefeated teams were the 1975 and 1976 Indiana Hoosiers. They lost in the tourney in '75 and gave Bob Knight his first championship by going undefeated in both season and tourney in '76.
The Dallas Cowboys have never had an undefeated season.
The Steelers have never had an undefeated season in their NFL history.