This is the 9933rd most frequent Russian word.
александрийцев
"Alexandrians" – people from or associated with Alexandria.
The word "александрийцев" is used in this sentence to denote inhabitants of Alexandria, functioning as a plural noun in the genitive case.
Многие александрийцев принимали участие в торжественном праздновании.
Many Alexandrians participated in the ceremonial celebration.
Here, "александрийцев" refers to people from Alexandria, used in the accusative case as the object of "считали" (were considered).
Во времена древности александрийцев считали одними из самых образованных людей.
In ancient times, Alexandrians were considered among the most educated people.
In this example, "александрийцев" functions as a possessive genitive to describe the culture belonging to Alexandrians.