[weinzierl]

It is the Hausnummer (building number). Every building has one and the signs have to fulfill certain requirements.

Usually they increase from the city center outwards, even numbers on the right side, odd numbers on the left.

We write them always after the street name, which drives Google Maps and other badly internalized software nuts.

Buildings don't have official names, some have informal ones, like the Gropius Bau.