noun which may take the genitive case particle 'no'
Indicates a small, indefinite number of countable things. Used as a noun or with の to modify another noun.
冷蔵庫に卵がいくつかあります。
There are a few eggs in the fridge.
いくつかの問題を解決しなければならない。
We have to solve several problems.
Please answer a few of the questions.
テーブルの上にリンゴがいくつかある。
There are a few apples on the table.
I bought a few souvenirs at the shop.
若干 is a more formal, written-style word for 'a small number/amount', while いくつか is the everyday spoken equivalent.
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 means 'many/a lot', the opposite quantity from いくつか's 'a few/several'.
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.