Arabic numeral: Cardinal number name | Ordinal number name, with conjugation information
1: Unus -a -um | primus -a -um
2: duo, duae, duo | secundus -a -um
3: tres, tria | tertius -a -um
4: quattuor | quartus -a -um
5: quinque | quintus -a -um
6: sex | sextus -a -um
7: septem | septimus -a -um
8: octo | octavus -a -um
9: novem | nonus -a -um
10: decem | decimus -a -um
11: undecim | undecimus -a -um
12: duodecim | duodecimus -a -um
13: tredecim | tertius decimus -a -um
14: quattuordecim | quartus decimus -a -um
15: quindecim | quintus decimus -a -um
16: sedecim | sextus decimus -a -um
17: septendecim | septimus decimus -a -um
18: duodeviginti | duodevice(n)simus -a -um
19: undeviginti | undevice(n)simus -a -um
20: viginti | vice(n)simus -a -um
30: triginta | trice(n)simus -a -um
40: quadraginta | quadrage(n)simus -a -um
50: quinquaginta | quinquage(n)simus -a -um
60: sexaginta | sexage(n)simus -a -um
70: septuaginta | septuage(n)simus -a -um
80: octoginta | octoge(n)simus -a -um
90: nonaginta | nonage(n)simus -a -um
100: centum | cente(n)simus -a -um
500: quingenti | quingente(n)simus -a -um
1000: mille | mille(n)simus -a -um
From Cassell's Latin English Dictionary, second edition.
Just like an English speaker sees "1, 2, 3, 4, 5, 6" and pronounces "one, two, three, four, five, six". Sure, the Roman numerals look like letters, but that doesn't mean you pronounce them that way.
In my opinion the important innovation of Hindu–Arabic numbers is not having different symbols for each digit, but rather using the same ten symbols (and no others!) for representing larger groups, which gives the system a lovely uniformity across numbers of different scales.
There aren’t many (if any?) human languages that duplicate this feature of being a purely positional system.
But of course, there's no way they actually said it that way.
Right? Right??