This is the 18221st most frequent Russian word.
четверых
"Четверых" means "four people" (in the accusative or genitive case).
The word "четверых" is used in the genitive for animate objects, describing the number of people being invited.
Он пригласил четверых друзей на ужин.
He invited four friends to dinner.
Here, "четверых" is used to indicate the number of people the meal is for.
Мы приготовили обед для четверых.
We prepared a meal for four people.
In this case, "четверых" is used in the genitive to enumerate passengers present in the vehicle.