German numbers have one distinctive quirk that surprises learners immediately: two-digit numbers are said with the units before the tens, reversed from English.
21 in German is einundzwanzig — literally ein (one) + und (and) + zwanzig (twenty), or "one-and-twenty." This reversed order applies consistently across German's two-digit numbers, so once the pattern clicks, it applies predictably rather than needing memorization number by number.
Hundreds and thousands attach in a fairly regular, additive way once the units-before-tens quirk is internalized — the underlying system is consistent, just organized differently than English's tens-before-units order.
German number order reverses English's pattern for two-digit numbers — einundzwanzig literally means "one and twenty," with the unit spoken before the tens, consistently across all two-digit numbers.
It applies consistently to two-digit numbers; larger numbers (hundreds, thousands) build additively on top of that same underlying pattern.
Not entirely unique, but it is a distinctive difference from English and many other languages that say tens before units, and it's one of the first things learners notice.
Yes, as core vocabulary content, matching the approach used in Tarc's existing courses.
See also: German Vocabulary · German Grammar · Learn German