Shanghai

• All counties of Shanghai has the code 21.
  
• The local phone number was changed to 8 digits by the end of 1995. The
  rule is: add 6 before the original 7-digit number if the first digit
  of the original number is 1-5, otherwise add 5 (e.g. 8xx-xxxx to
  58xx-xxxx, 3xx-xxxx to 63xx-xxxx).
  

21

Shanghai