How to create a WP user automatically

Situation:

Have WP installed.. with wildcard domain mapping via dns pointed to WP site..

I am not using WP Multisite.. as i don’t have a need for it…

Will be sending emails to prospects on my list to signup..

Each email will have a unique url for each user…

Example: 3442342.domain.com and 9797233.domain.com …. XXXXXXX.domain.com

So as each user clicks through to their unique url.. upon landing at the home page of XXXXXXX.domain.com I am wanting to present them a basic user registration form… with a hidden input field with the value of the subdomain id XXXXXXX

Upon clicking submit the user will have been entered into WP usertable and a confirmation link will be sent to them… to activate the user account..

The problem i am facing:

After reviewing and trying numerous samples via google search.. none of which actually work…

I need to be able to create X number of wordpress users on the fly upon the user landing at a unique subdomain and completing the registration page.