Penn State actually has 42 bowl appearances, Ohio State has 41, and Michigan has 39.
Part of the reason that Penn State may have more bowl appearances was that from 1918 to 1945, Big Ten Teams were not allowed to participate in bowls. From 1946 to 1974, only the conference champion could go to a Bowl, but not for two consecutive years. Penn State, being an independent at the time, was not tied by the same constraints.
Michigan has 11 National Championships, Ohio State 7, and Penn State 2.