30 « Latin for Addicts

There are four central aspects to the Latin numeral:

The numerals 11-19 are indeclinable:

note that 18 and 19 start counting back from twenty, while the others count up from ten
French and Spanish (and other Romance languages?) also seem to freak out and shift form somewhere after 15; I’m not sure why no one thought a standardized 11-19 was a good idea

The numerals 20-100 are expressed as follows; bases of ten do not decline:

To achieve a number like 85, the Romans have two preferred methods:

tens+ ones= (octōgintā quīnque mīlitēs)
ones + et + tens =(quīnque et octōgintā mīlitēs)
note that octōgintā et quīnque (a third option) is less common, but may appear
also, note that numbers like 28 and 29 nine subtract as 18 and 19 above: duodētrīgintā, ūndētrīgintā, ūndēoctōgintā (79), etc.

The hundreds above 100 decline as adjectives like bonus, bona, bonum

Mille is an odd bird: it’s indeclinable as a singular (mīlle mīlitēs) but declines as a neuter plural (tria mīlia mīlitum)

Note that there’s no typo here (though I am prone to typos): the singular mīlle has two l‘s; the plural mīlia/mīlium/mīlibus/mīlia/mīlibus has only one.
He came with a thousand soldiers: cum mīlle mīlitibus vēnit.
To express this sentence with three thousand, we decline tria mīlia and make mīles a partitive gentive
He cam with three thousand soldiers: cum tribus mīlibus mīlitum vēnit.

To express numbers with three digits or more:

If et appears anywhere, it appears only between the two highest demoninations:

Latin for Addicts