This is the 275th most frequent Croatian word.
broju
"Broju" is the dative or locative singular form of "broj," meaning "number."
Here, "broju" is the dative case of the noun "broj" (meaning "number") and is used to denote the indirect object of the verb, identifying the phone number to call.
Molim te, nazovi me na mobitel po broju koji sam ti dao.
Please, call me on the mobile number I gave you.
In this sentence, "broju" is also in the dative case following a prepositional construction, denoting the numbered spot or label that the person will approach.
Kad dođeš na red, prići ćeš broju na šalteru.
When your turn comes, you will approach the number at the counter.
Here, "broju" again takes the dative case to indicate association or reference within the prepositional phrase, pointing to the context of the change.