Turkey plate and area codes
The Turkey license plate codes table lists all 81 provinces, from 01 Adana to 81 Düzce, with their region and phone area code. Codes 01 to 67 were assigned in alphabetical order to the provinces that existed at the time, and newer provinces received the next free numbers. The Turkey area codes tool lists landline codes for every province, mobile prefixes by operator and the +90 format you need to dial a Turkish number from abroad.
Turkish ID number validator
A Turkish identity number (TC Kimlik No) has 11 digits, and the last two are calculated from the first nine with a fixed algorithm. The validator recomputes those check digits to tell you whether a number is formally valid, which is useful for developers building form validation and for anyone doing data entry. A number that passes the check does not prove it belongs to a real person; the tool does not connect to any official database.
Spanish DNI and NIE letter
The final letter of a Spanish DNI is determined by the remainder when the eight-digit number is divided by 23. The calculator works out that letter and also supports NIE numbers issued to foreign residents, whose leading X, Y or Z is converted to a digit first. It is handy for checking forms and spotting typos before submitting documents. All calculations run in your browser, and the numbers you enter are never stored or sent to a server.