Number nine from the Arabic writing system hasn't changed during all these years. It has reached us in the form close to the original. At first, nine used to be expressed with a gesture where you make a fist with a thumb leaned aside. In ancient documents, it looked like a circle with a "tail" slightly turned to the right. Later on, the "tail" changed its position and curved to the left. 

We have been using such a nine for many centuries in a row, including in typography. One of the Unicode characters is Circled Sans-Serif Digit Nine enclosed in a circle. It is used as [URL /en/unicode/blocks/dingbats/ dingbat] along with other icons of similar design: [U:2787], [U:2786], [U:2785], [U:2784], and so on.