What is the numeric range of a 16 bit two's complement?

It's range is from: -32768 to: 32767. You can get to those values from (215)-1 for positive and (215) for negative. The sixteenth (first from the left) bit is the number's signal. The positive values have one less in range because of the representation of zero.

Check here for other bit depths: http:/escumalha.com/Binary.html