There are two systems of numbers in Korean which are Korean Numbers (Native Korean) and Chineese-derived Numbers (Sino Korean). Korean numbers are used mostly for counting, while Chineese numbers are used for reading the numerals. However, for the numbers one hundred and above, Chineese numbers are used.
In Native Korean, to express let say 11 it’s 열하나 (yeol-hana) so the formula is 10 (열) + 1 (하나). This is also applied to the numbers 20-99. You have to memorize at least 18 numbers in Native Korean [1-9 and the multiple of 10 from 10 to 90].
While in Sino-Korean, to express let say 32 it’s 삼십이 (sam-ship-i) so the formula is 3 (삼) X 10 (십) + 2 (이). There are few numbers to memorize in Sino-Korean, with just 13 numbers to you can go up to a million already.
