How many regions in OSM ?


I want to know the number of regions inventoried in OSM. These regions would correspond to the administrative level equal to 4.
This web site classifies administrative levels by country but is not available.

To start, I tried to use osmconvert by extracting the zone africa but I get the names of the cities and not the names of the regions with this :

> osmfilter africa.osm --keep="admin_level"="4" > africa_adm4.osm
> osmconvert africa_adm4.osm --all-to-nodes -csv="@id @lat @lon name" --csv=headline > africa_adm4.txt

Do you have an idea to know the number of regions (administrative level = 4) in OSM?

Thank you in advance !

We expect the webservice of back in some days, I hope.