Super Math Challenge Problem, Help!?

At Schnortzville High, there are lockers uniquely numbered from 1 all the way to 500. Suppose the first of 500 stick figures opens each locker, but then the second stick figure closes every second locker. If the third stick figure changes the state of every third locker (open locker become closed, closed lockers now open), the fourth stick figure does the same with every fourth locker, and this continues until the last stick figure alters the state of locker #500, how many lockers are open at the end?