Hebrew numerals. Roman numerals. Arabic (Indian) numerals.
What numbers can a Jew use? What numbers should he use?
How should pages in a ספר קודש be numbered?
הישיבה הרמה בפיורדא relates (volume II, p. 116-118) that the number system that is widely used nowadays, generally referred to as Arabic numerals, came relatively late to Jewish use. Rav Yaakov Emden was a pioneer in utilizing them in a sefer kodesh, by doing so in his famed siddur, the first volume of which, עמודי שמים, was printed in 5505 (1745 C.E.) in Altona. This page in the siddur is one illustration.
Some Hungarian Rabbis opposed such usage, even going so far as to say that it was אסור, as it did not come down to us from הר סיני, as R. Shaul Brach argued.
However, the author notes, they have become widely accepted nowadays, and are seen in many seforim. He also comments in a footnote, that they can be seen at times in works of the Chasam Sofer (of חדש אסור מן התורה fame) himself.