Can a broken prong stuck in an outlet increase electrical consumption?
A prong by itself cannot make a complete circuit. Even if it did, it would immediately trip your circuit breaker and likely damage the receptacle (as in it would visibly spark/arc). It doesn't sound they they're on the surface either, or they would be a shock hazard.

If I were you, and you feel confident enough to turn the power off, you could replace it easily with a new receptacle. It's just a matter of unscrewing and screwing with wires. Take a picture of the wires before you disconnect them.