54 The Luhn algorithm for verifying credit card numbers, etc 2011-01-27T21:43:32.773

33 Is my barcode valid? 2017-11-15T15:19:41.803

32 Compute the Adler-32 checksum 2016-04-30T05:17:15.233

28 Calculate ISBN-13 check digit 2011-02-01T18:58:11.477

21 Converting ISBN-13 to ISBN-10 2018-01-19T18:50:22.580

18 Generate a parity bit 2016-04-25T23:26:36.360