Area Code Nanjing
The prefix 25 is the area code for Nanjing. And Nanjing is located in China. If you are outside United States of America and you want to call a person in Nanjing, in addition to the area code, you need the country code for the country you wish to call. The country code for United States of America is +86, so if you are in United States of America and you want to call a person in Nanjing, you have to prefix that person’s phone number with +86 25.
The zero in front of the area code is omitted in this case.
The plus sign at the beginning of the phone number can usually be used in this format. However, it’s more common to replace the plus sign with a sequence of numbers that alerts the telephone network that you want to dial a telephone number in another country. The ITU recommends using 00, which is also used in many countries, including all European countries.
In United States of America, 011 is used instead of 00.
As an alternative to +86 25, which you have to place in front of the telephone number of a person in Nanjing in order to call them from United States of America, you can also use 01186 25.
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