하나 - one

둘 - two

셋 - three

넷 - four

다섯 - five

여섯 - six

일곱 - seven

여덟 - eight

아홉 - nine

열 - ten

So

열하나 - 11

열둘 - 12

열셋 - 13

열넷 - 14

And so on

둘열다섯 is wrong. There is a word for 둘열 and that is 스물. Its like twenty, thirty, fourty etc of english.

20 - 스물 [seu-mul]

30 - 서른 [seo-reun]

40 - 마흔 [ma-heun]

50 - 쉰 [swin]

60 - 예순 [ye-sun]

70 - 일흔 [ir-heun]

80 - 여든 [yeo-deun]

90 - 아흔 [a-heun]

So 스물하나 = 21

서른셋 = 33

마흔넷 = 44

And so on

Remember not to write 100 = 하나백, 1000 = 하나천, 10,000 = 하나만. Don't write 하나 with it. The word 십, 백, 천, 만 are enough alone.

And yes 백, 천 and 만 are common for both systems BUT there is no 둘, 셋, 넷 or any before a 백/천/만 to show 200, 3000, 40000- nope

Always write a sino korean number before the 백/천/만.

삼백 = 300

이백다섯 = 205

사만여덟 = 40,008

육만오백스물한 = 60,521

Lmaoooo its so hard- kill me