Among them, the small cube coated on three sides: as can be seen from the figure, it is the small cube where the eight corners of the big cube are located, that is, eight small cubes are coated on three sides.
Double-sided painting: only at the intersection of two sides, that is, only on 12 shuttling cubes, and only one small cube on each side intersects with two sides, so there are 12 such small cubes.
One side painting: one side of the painting does not intersect with other sides. Obviously, there is only one small cube in the middle of each side that does not touch, so there are six such small cubes.
Unpainted: * * There are 27-8- 12-6= 1, that is, the central block of the big cube is unpainted.