Not a historian. They had a different numeral system. The Roman one is pretty well known. They used

I=1

V=5

X=10

L = 50

C = 100

D = 500

M = 1000

They combined those to write numbers, by adding and subtracting.

E.g 2956 was MMCMLVI, where MM means 2000 (each M means 1000), CM means 900 (C means 100, put before M means 100 less than 1000), L means 50, and VI means 6 (V means five, I means 1, when put after 5 means '1 more than 5')

Thus MM + CM + L + V + I = (1000+1000) + (1000-100) + 50 + 5 + 1 = 2956

We still use them to an extent, for example in movie posters ("Rocky V") or names of popes (Pope Benedict XVI) and more on as listed on Wikipedia

Ancient Greeks had their own system as well. Just like Romans they used their alphabet letters to represent numbers. On the other hand, their system was closer to the Arabic, as there was a single symbol for 1-9 . Different from the Arabic they had a single symbol to represent 10, 20, 30...100, 200...900. They too added them, like Romans did, but they did not subtract.

E.g 256 was σνϝ where σ = 200, ν=50 and ϝ=6, thus σ + ν + ϝ = 200 + 50 + 6 = 256