Are there runways that are numbered only on one side?
Yes, there are runways numbered on only one side. 

For example, the third runway in the Frankfurt Airport (18, Runway west) is used only for takeoffs (to the south) and not for landings. Hence only number 18 is used. The other runways are used for both takeoffs and landings and are numbered 07C/25C, 07R/25L and 07L/25R.

Thomas Römer/OpenStreetMap data [CC BY-SA 2.0], via Wikimedia Commons

This restriction is due to the fact that it will interfere with the traffic in other runways.

Number 36 is not painted.