The V2 has 6 touch sensors, 2 Audio sensors and 3 IR Receivers. I'll break them down by body part.

Head

3 IR Receivers - These are used to decode the signals from the remote, and may also be linked in to his object detection / avoidance.
2 Audio Sensors - These sensors sense sharp noises and determine there which side of the robot they came from.

Left / Right Hand

1 Touch Sensor - Each hand has a touch sensors for detecting obstacles and for triggering his programs.

Left / Right Foot

2 Touch Sensors - Each foot has 2 touch sensors for detecting obstacles and for triggering his programs.