Hebrew letters also serve for number. A table comparing Hebrew, Greek and Slavonic number is presently here, although the page notes that they have used non-standard forms for the Hebrew numerals 15 and 16 to avoid resemblance of the pair to the form of the Holy Name. The same site also treats ways of writing the years:-
writing Latin numbers
Arabic numbers were treated with reserve in some quarters even as late as the mid-fourteenth century, when this image (left) shows them identified, still, with a ‘Saracen’ character. The painter was clearly an arch-conservative; by this time Hindu-Arabic numerals had been in daily use for more than a century.
The Encyclopaedia Britannica notes a variant form of Chinese numerals used by merchants, but does not specify its date:
There was more than one system for Greek numerals. On these and on the Latin, Thompson’s book is still good.
Edward Maunde Thompson, An Introduction to Greek and Latin palaeography (1914). link is to the copy at archive.org. (Number and numerals pp.91-2).
“The power of number is this: that all things have been formed in its likeness.”
– Hugh of St.Victor, Didascalion, Bk.II ch.6. link is to the full text at archive.org.
On the significance accorded number in medieval Europe, the foundation text is still
Vincent Foster Hopper, Medieval Number Symbolism. Its Sources, Meaning and Influence on Thought and Expression. First published in the 1930s, and later reprinted by Dover Books, it is still available in hardcopy though not in digital form. The following paragraph from a review by Solomon Gandz.