also: いくたり
expression
Used to ask about the number of people. The reading いくにん is more common in modern Japanese; いくたり is a traditional counter reading that may appear in literary or formal contexts.
パーティーには幾人来ますか。
How many people are coming to the party?
この部屋には幾人入れますか。
How many people can fit in this room?
Mixed kanji-kana spelling, common in everyday writing.
何人 is the most common way to ask 'how many people' and is more neutral in register. 幾人 is slightly more formal or literary.
Compound of 幾 (iku, 'how many') and 人 (nin/tari, counter for people). The reading いくたり uses the traditional counter たり, which is now largely replaced by にん.