When you search dictionaries for “two”, you would know the word “two” can be an adjective. In some dictionaries it is a determiner. The determiner is newer concept and words used to be adjectives.

For example, red, big, long etc are adjectives. The Earth is red. Is that indeed true? “two” is a adjective. Which is, if not identical by definition, can you see any two examples of adjective? Why do we say there are two reasons?