Yes it would be very unhealthy to cut down that much, not to mention slow down your metabolsm and make it to where you will burn into your muscle and keep all that yummy fat. If you need 2100 then cut back by 500 to 1600.
It takes 3500 calories cut to lose a pound. So every week at that weight you will lose a pound possibly a little more if you are combining it with cardio and strength training. And also the more you weight, the more it all shocks teh system so it could be up higher than that. You should never go below 1300 calories no matter who you are.