Photo credit: TurtleDiary.com
Battle of Factors can be fun for fans of Star Trek, as students fire (with photon torpedoes?) at ships that have the factors whose product equal the listed product. They must do this before the ships get close enough to destroy your ship.
Disclaimer: this game does have shooting in it. TurtleDiary also used to be free, but it looks like they are now providing some brief sample plays of their games, then charging fees.