Audit a Twitter account to see the number of real and fake followers. The service is free for this and has a paid version for more advanced features. You can also see the Quality Score Per Follower.
Analysis of a username’s Twitter followers including where they are from, when they are most active. They also have whats called “Social Authority” to see a user’s influence and engagement on Twitter. It ranges from 1 to 100, where higher scores indicate a person with greater influential activity.