What is ISBN? The copyright pages of regular books all have ISBN numbers. ISBN is the abbreviation of ISBN, that is, ISBN. It consists of 10 digits and consists of four parts: group number, publishing house number, book name and inspection number, which are connected by "-",such as ISBN978-7-560 1-3496-3. The group number represents the language of a country or region. The publishing house number is the code name of the publishing house, which is set and assigned by the ISBN center of a country or region, and can be 1-7 digits. The title of the book is the number given to each publication by the publisher. The check code is the last digit of the ISBN number, which can be used to check whether the ISBN number is correct, that is, the number of ISBN 1-9 is multiplied by the nine digits of 10-2 in turn, and the check code is added to the sum of these products. If it can be divisible by 1 1, the ISBN number is correct. The formula is 7 *10+3 * 9+0 * 8+5 * 7+0 * 6+1* 5+5 * 4+6 * 3+8 * 2+7 =198,198. The check number can only be 1 digit, and when it is 10, it is recorded as Roman numeral X.