Note that when combined with a counting word, the last letter of numbers 1,2,3,4 as well as 20 is dropped:
Example: 1 means hana in korean pure number, na magiging hanmyeong siya kapag naicombined na si myeong which is counting word for person.
One person : Hana+myeong = hanmyeong
Three things : set + gae = segae
Twenty things : seumul+ gae= seumugae
Ganon lang po. Natatanggal ang last letter ng number.