The rule
German says the ones before the tens: 21 is ein-und-zwanzig — literally "one-and-twenty". It feels backwards for a long time, and then it does not.
The pairs that catch everyone out
| 21 | einundzwanzig |
|---|---|
| 12 | zwölf |
| 27 | siebenundzwanzig |
| 72 | zweiundsiebzig |
| 100 | hundert |
| 1000 | tausend |
27 and 72 are the same two words in the other order. When a number matters — a price, a platform, a house number — ask „Noch einmal, bitte."