Divisor shows you how much each item in a stack costs at the auction house. For example, if there were 5 motes of fire available for a 12g 50s buyout, Divisor would inform you that each mote of fire would cost you 2g 50s, and that 10 of them would cost you 25g.
For WoW Classic versions (Classic Era, Burning Crusade, Wrath) only.