Years ago I read about a German word that meant "unusual or special number." Examples were given as 12345, 9861689 (numerical palindromes), 2468, and such. I cannot find anything like this on line and am wondering if I was tricked.
I guess you're searching for the word Zahlenmuster which means that the numbers do have a specific regularity.
There are also some math lessons where children have to search for so called ANNA, TILL and NANA regularities. ANNA numbers would be something like 8228, 9449, TILL numbers are something like 1233, 6788 and NANA numbers are something like 6767, 4545.
Zahlenpalindrom would be the word for numbers like 862268 whose number system has the same value read from the front and back.