Newer Android phones have auto updated to android OS 6.  Brand new phones are running version 7.
BUT- the bulk of existing (older than 2 year) android phones (AND ANDROID TABLETS) are running earlier versions and will NOT be updated/supported  by their manufacturers.
I don’t see good antivirus programs running on android.  I have Avast Mobile Security,  on my 1 year-old android phone, which appears to do at least some real-time monitoring, and scans once a week or so.
I don’t know if this is adequate for older android devices.