How long does it take to receive the patent number by patent mail?

Once and for all, nearly two weeks. It also depends on where you are, whether you use surface mail, registered mail or express mail of the postal system, which all affect the time. If it is mailed, the postmark date of the mailing date shall be the date of patent application.

Why send it to Beijing? You can submit an application at your provincial intellectual property office, and it may be faster to get the acceptance notice.

If an agency is required to make an electronic application, it can get an electronic acceptance notice on the same day and a paper acceptance notice sent by the State Administration a week later.