What comes after 19?

After 19 comes 20. In the base-10 numbering system, numbers are organized in a sequential order from 0 to 9, and then the next number is formed by adding a digit in the tens place and resetting the units place to 0. So, after 19 (which is composed of 1 in the tens place and 9 in the units place), the next number is 20 (with 2 in the tens place and 0 in the units place).