This is the 16873rd most frequent Turkish word.
çep
The Turkish word "çep" refers to the "edge" or "rim" of something.
Here, 'çep' is a colloquial abbreviation of 'cep', referring to 'cellular' as in 'cell phone'.
Çep telefonunu yeni aldı.
They just bought a new mobile phone.
In this context, 'çep' again stands for 'mobile' or 'cellular', commonly used to refer to a mobile phone number.
Çep numaranı paylaşabilir misin?
Can you share your mobile number?
'Çep' used here colloquially refers to the 'pocket' of clothing, a less formal variant of 'cep'.