Number words are adjectives. Every time you put a number word with a noun, you are using an adjective.
I bought two ears of corn at the market.
We need five potatoes for dinner.
Bobby read twenty books during the summer.
My neighbor has three noisy dogs.
A number word modifies the noun when placed in front of the noun. That makes the number word an adjective.
▶Now you try it. Find the number word adjective in this sentence. I brought three cookies in my lunch so I can share with you. That wasn’t too hard, was it?