There's no way to apply track numbers to a batch of songs, but you can make short work of adding them one at a time by using the Next button in the Info window. After typing "1" on the first track, click Next. Your cursor remains in the Track field so you can type "2" and click Next, and so on. Very quickly you'll have all the tracks in the album numbered.
Now you can select all of them and apply the total number of tracks if you wish, so that the library will show "Track N of N."
If only iTunes had an option in the playlists like, "Renumber tracks as shown."