[redirect] redirect url plugin with special feature

Hi,
I want to do redirect service on my site. There are few conditions it must apply.
1) My site is abc.com. If anyone just do something like this, abc.com/60123456789 the site will redirect to https://api.whatsapp.com/send?phone=60123456789. They do not need to setup anything at all. All link will get redirected.
2) It will only redirect if the link start with number 6. if user put in abc.com/1 or abc.com/a it will show up error 404 page. if the starting is abc.com/6xxxx then it will get redirected.
3) let me know if there is plugin for this.
thanks