However it is not clear how many of these accounts’ followers are real people and how many may be fake accounts.
Searches using the tool Twitter Audit – which analyses a sample of followers and calculates a score based on factors including the number of tweets they have sent – suggested that about two-thirds of both Perry’s and Bieber’s followers may not be real.
For Mr Obama and Mr Trump the figure dropped to about a third.
In January researchers in the UK discovered massive collections of dormant fake Twitter accounts.
Some had been used to fake follower numbers, send spam and boost interest in trending topics, the researchers found.
Twitter says users are banned from writing programs that automatically followed or unfollowed accounts or which “favourited” tweets in bulk.