Learn French: Cette ville a deux mille habitants. - This town has two thousand inhabitants.

In French, the number mille (thousand) is invariable, meaning it never changes form. Even though it is plural here, it never takes an s. Watch out, because million and milliard are considered nouns and do take an s in the plural (like deux millions).

Can I write deux-mille with a hyphen?

Yes, you can. Traditional French spelling uses a space, but the 1990 spelling reform allows hyphens between all words in a compound number. Both deux mille and deux-mille are completely correct.

Since habitants starts with an H, do I need to make a liaison with the word before it?

The h in habitants is indeed a silent "h muet", which usually allows for a liaison with the preceding word. However, because mille already ends in a pronounced consonant sound (the L sound), there is no extra liaison letter to sound out. You just transition smoothly from the L sound directly to the A sound in habitants.

Why use ville (town) instead of village here?