You can check registration status of a consumer using pulp-consumer status command. With this command you can get the information about which server the consumer is registered to and the consumer id used for the registration.
$ pulp-consumer status This consumer is registered to the server [test-pulpserver.rdu] with the ID [f17-test-consumer].
When the consumer is not registered to a pulp server, it will simply display a message stating the same.
$ pulp-consumer status This consumer is not currently registered.