The numbers 11 and 12 are irregular.
From 13, the formation of the numbers is mostly regular. In German, the order of numbers is opposite to that in English. First comes the single digit (e.g. drei, vier, fünf...) and then the ten (zehn):
The numbers 16 and 17 are slightly irregular. The single digits (sechs, sieben) lose their endings.
| 11 | elf | |
| 12 | zwölf | |
| 13 | drei + zehn | dreizehn |
| 14 | vier + zehn | vierzehn |
| 15 | fünf + zehn | fünfzehn |
| 16 | sechs + zehn | sechzehn |
| 17 | sieben + zehn | siebzehn |
| 18 | acht + zehn | achtzehn |
| 19 | neun + zehn | neunzehn |