The most interesting exotic numeral systems I know of are Cistercian numerals [1] and Indic [2] and Ottoman [3] Siyaq numbers. The latter two were even added to Unicode 14.0 [3][4], but not many fonts support them.<p>[1]: <a href="https://en.m.wikipedia.org/wiki/Cistercian_numerals" rel="nofollow">https://en.m.wikipedia.org/wiki/Cistercian_numerals</a><p>[2]: <a href="https://en.m.wikipedia.org/wiki/Indic_Siyaq_Numbers" rel="nofollow">https://en.m.wikipedia.org/wiki/Indic_Siyaq_Numbers</a><p>[3]: <a href="https://en.m.wikipedia.org/wiki/Ottoman_Siyaq_Numbers" rel="nofollow">https://en.m.wikipedia.org/wiki/Ottoman_Siyaq_Numbers</a><p>[4]: <a href="https://unicode.org/charts/PDF/U1ED00.pdf" rel="nofollow">https://unicode.org/charts/PDF/U1ED00.pdf</a><p>[5]: <a href="https://unicode.org/charts/PDF/U1ED00.pdf" rel="nofollow">https://unicode.org/charts/PDF/U1ED00.pdf</a>