The first three digits represent the operator, the fourth to seventh digits represent the city where the number belongs, and the last four digits are the customer number. This method of analyzing numbers is based on the five elements and the congenital number of river maps, which originated from the Book of Changes of our ancestors for 5000 years. Numbers are calculated with "1 6" as water, "2,7" as fire, "4,9" as gold, "5,0" as soil and "3,8" as wood.
Roman numeral
On the basis of Greek numerals, the Romans established their own counting methods. Romans used letters to represent numbers, I for 1, V for 5, X for 10, C for 100, and M for 1000. Such a large number is relatively short to write, but it is still very inconvenient to calculate. So today people seldom count with Roman numerals, but sometimes they can be seen to be used in year numbers or clocks.