16
if you mean "vertices" by "corners" then sixteen
Corners
16
24 but note that if you piled the 3 cubes on top of eachother, you could make them into a single rectangular solid having only 8 corners.
A rectangular prism that is 4 cubes by 2 cubes is made up of 8 cubes.
They have 16 corners.
10 corners
2 cubes wide x 3 cubes long x 4 cubes high. 2 X 3 X4 6 X 4 24 cubes
2 sides, 2 corners. (:
There are 12 squares on 2 cubes
24 cubes would be it.