There are many different signs that the API Developer Portal 4.x tells us its version but a simple and sure method is described in this article.
How can we check the version number of our current installation of API Developer Portal 4.x?
Please login to the API Developer Portal 4.x host with SSH and type the following rpm command. ("$" is a prompt here)
$ rpm -q apim-portal
The result for v4.0:
For v4.0.170601 Patch: