en.wikipedia.org/wiki/Telephone_numbers_in_China

The article lists Yanbian as 4331, but official Jilin government sources show Yanbian contact numbers using the 0433 area code. In domestic shorthand that is 433. So 4331 is wrong; the final 1 appears to be a footnote marker accidentally attached to the area code.

This entry lists Pu’er as 87930, but official Yunnan government material shows Pu’er telephone numbers using the 0879 area code. In domestic shorthand that is 879. So 87930 is incorrect; the trailing 30 is a footnote number that has been merged into the area code.

This line lists Xinyang as 3762, but official Xinyang government material shows local telephone numbers beginning with the 0376 area code. In China’s domestic area-code notation, that is 376. That means 3762 is wrong, with the trailing 2 apparently coming from a footnote marker rather than the actual code.

The page lists Suzhou’s area code as 5121, but official Suzhou government contact information uses telephone numbers with the 0512 area code. In domestic shorthand that is 512. So 5121 is incorrect; the extra 1 is not part of Suzhou’s area code.

This entry lists Harbin’s area code as 4511, but official Heilongjiang government material shows Harbin telephone numbers using the 0451 area code. In China’s domestic area-code tables, the leading 0 is often omitted, so the correct area code is 451, not 4511. The extra trailing 1 appears to be a footnote number that was accidentally merged into the code.

The article shows 3711 for Kaifeng, but the Henan provincial government’s administrative information lists Kaifeng’s telephone area code as 0371. In domestic shorthand, that is written as 371. So 3711 is incorrect; the final 1 is not part of the area code.