Luhn algorithm - Calculate check digit

Calculate check digit using the Luhn algorithm.

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The Luhn algorithm, a simple checksum verification algorithm, is also known as Luhn formula, modulus 10 algorithm, or mod 10 algorithm. It is most notably used to validate credit card numbers and IMEI phone identification numbers.

enter numbers only, without check digit
0 digits
calculated, with trailing check digit
0 digits

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