いくつか

Meanings

noun which may take the genitive case particle 'no'

usually written using kana alone

Indicates a small, indefinite number of countable things. Used as a noun or with の to modify another noun.

いくつかの〈物もの〉several/a few of (something)
いくつかの質しつ問もんに答こたえてください。
Please answer a few of the questions.
〈物もの〉がいくつかあるthere are a few/several of (something)
テーブルの上うえにリンゴがいくつかある。
There are a few apples on the table.
〈物もの〉をいくつか〈動どう詞し〉to (verb) a few of (something)
店みせでお土産みやげをいくつか買かった。
I bought a few souvenirs at the shop.

数すう個こ
数個 explicitly emphasizes counting a small number of discrete objects, while いくつか is vaguer and can also modify abstract or countable nouns without stressing the count itself.
いくらかN2
いくらか can describe an indefinite small amount of either countable or uncountable things, whereas いくつか is used only for countable items.
若じゃっ干かんN2
若干 is a more formal, written-style word for 'a small number/amount', while いくつか is the everyday spoken equivalent.
一いち二に
いくつか is a colloquial general word for 'a few (of something)' usable on its own, while 一二 typically attaches directly before a counter, as in 一二日.

たくさんN5
たくさん means 'many/a lot', the opposite quantity from いくつか's 'a few/several'.

いくつも
いくつも means 'quite a few/many' with an emphatic nuance, while いくつか simply means 'a few/some' without emphasis on quantity.
いくらかN2
いくつか sounds similar but means 'a few/several (countable items)', while いくらか refers to an unspecified amount or degree, often uncountable.

Combination of いくつ (how many) and the question particle か, which here functions to create an indefinite expression.