Darrell Davis added 15 points and Kendall Pollard scored eight with 10 rebounds for Dayton, which opened the game with an 11-0 run and never trailed, shooting 51.9 percent from the field. Mikesell, whose 21 points are the third-most scored in a game by a Dayton freshman, also had eight rebounds and four assists.
The Flyers held Southeastern Missouri State to just 16 points in the first half and took a 30-point lead into the locker room.
Marcus Wallace led Southeastern Missouri State with 12 points and seven rebounds.
The Redhawks shot just 31 percent from the field, including 5 of 25 from 3-point range, and 35 percent (8 of 23) from the free throw line. They were outrebounded 52-36.