To change admin default username in wordpress is a little bit tricky. Especially when you already setup it and running the wordpress for a while.
But there is a way to do it. Here is how according to this source.
- You need to access your database of the wordpress. So I am talking about hosting your wordpress domain, not a free wordpress.com account.
- Use phpmyadmin or else that the hosting provider provide, to access the database.
- Edit the wpxxx_users data and change the name of the ‘admin’ to ‘mynewuser’.
- Edit the wpxxx_sitemeta and change the value of the site_admins row. It might look different but change the name admin to mynewuser, don’t forget to change the number in front of the admin name. Admin is 5 characters that is why the number is 5. If you use mynewuser, it means you use 9 characters. So change it to 9.
Login to your wordpress with mynewuser login name.