Are you sure you are comparing apples and oranges here? Google market numbers are unique settings. One installation can lead to a very large number of visits, for example, someone installed your application immediately after its launch and visited it every day (or even several times a day). This will be considered “1” for market statistics and as much for analytics. You can select the "New Visitors" advanced segment in analytics, and this should be much more comparable.
Another explanation may be that you or someone else posted your APK on an alternative market or somewhere on the Internet, and the people who get it are tracked by analysts, but, of course, not by market numbers.