Changing user name from Admin and stopping hackers

Hi,

I am aware that the most common answer to my problem if not the only one is that I cannot change my user name from ‘Admin’ to something else reason being, I believe, is that I self host my website.
That said I would like to know if there is anyway of changing it from ‘Admin’ to a user name of my choosing. It just seems idiotic that I cannot choose my user same.
My second problem is that I have a lot of hackers creating a user name in my account (website). How can I stop this from happening?
I feel that is is directly connected to the fact that my user name is ‘Admin’ which leaves hackers with needing only to find my password to hack into my website since most commonly any given user name will probably be ‘Admin’.
So if anyone could help me change my user name and provide me with a solution to stop hackers from creating accounts on my website I would very much appreciate it and sincerely thank you for your help.
Thanks for your time.