The numbers beside a users name is called their "Karma". It reflects how much good the user has done in the community in terms of having their posts up-voted or down-voted, friends they've added, statistics they've had verified and other beneficial activity.
Of course! You can try and get Karma by posting informative and useful information and sharing it, making new friends, inviting people that you know.
Or you can look at obtaining Karma in a more altruistic manner, by just simply being a good user.
In the same way you can receive good Karma by posting informative content, you can also receive negative Karma points by having people in your network remove you, people disliking your posts, having messages reported or your profile down-voted.
Can I buy Karma?
Just as in real-life you can’t buy karma, you can’t on this platform either. Karma can only be accrued from good actions.
How can I get rid of negative Karma?
As in real-life again, do good. Make positive contributions. Be a constructive member of the community. You’ll earn great karma - both here, and in the real world.