Mental Manipulation: Folding the Net

Here is a cube net described in words. Four squares are joined in a single vertical column, labeled 1, 2, 3, 4 from top to bottom. Attached to the left of the second square from the top (2) is a square labeled 5, and attached to its right is a square labeled 6. You fold this net into a cube.

Fold the net up one face at a time in your mind. What number is on the face directly opposite the face labeled 1?