How to count total number of properties in a graph?

[lingvisa (Martin Min)]

I know how to count the nodes and relationships in the graph. What about properties? Is this the correct answer?

match (n) 
unwind keys(n) as key
return count(*)

[intouch_vivek (Vivek Srivastava)]

Yes this is the correct answer.
Reference

[webtic (Paul Jongsma)]

As noted in the reference; CALL db.schema.nodeTypeProperties() might be useful too.