Why do you add "+86" before the other party's mobile phone number when you receive a text message?

Problem description:

That is, when you receive a short message from the other party, you can see who the sender is, and the other party's mobile phone number is preceded by "+86", that is, the sender becomes "+8613 * * * * * *"?

Analysis:

+stands for international prefix, just like dialing+or 00 when making an international call with a mobile phone, and 86 stands for China. When calling back from abroad, you must dial +86 or 0086 first, which can generally be omitted in China, but it doesn't hurt to add one, so that the phone number is unique and complete in the world.