This is the 898th most frequent Russian word.
заявок
The word "заявок" is the genitive plural form of "заявка," meaning "applications" or "requests."
In this case, 'заявок' refers to the applications that have been received, specified in context, in genitive plural form as it relates to 'the number of.'
Количество поступивших заявок превысило ожидания.
The number of received applications exceeded expectations.
Here 'заявок' stands for applications being processed, again in the genitive plural form but in the context of receiving action from the subject.
Обработка заявок занимает у нас несколько дней.
Processing the applications takes us several days.
The word 'заявок' is used to indicate 'applications,' typically for an event or participation, and is in the genitive plural form to signify 'of applications' in the context of quantity.