adverb
Used to ask about a countable number of things. Can also be used in statements meaning 'several' or 'a few' when not in a question.
りんごはいくつありますか。
How many apples are there?
いくつか質問があります。
I have a few questions.
adverb
Used to ask someone's age, often in a slightly indirect or polite way. Common with children or when age is uncertain.
お子さんはいくつですか。
How old is your child?
彼はいくつになっても元気だ。
No matter how old he gets, he's still energetic.