11 is read as "eleven" and written as "11".
12 is read as "twelve" and written as "12".
13 is read as "thirteen" and written as "13".
14 is read as "fourteen" and written as "14".
15 is read as "fifteen" and written as "15".
16 is read as "sixteen" and written as "16".
17 is read as "seventeen" and written as "17".
18 is read as "eighteen" and written as "18".
19 is read as "nineteen" and written as "19".
20 is read as "twenty" and written as "20".