This is the 15243rd most frequent Russian word.
портативной
Portable.
In this sentence, 'портативной' is an adjective that modifies 'устройство'. It describes the device's quality of being portable.
Устройство является портативной и удобным.
The device is portable and convenient.
Here, 'портативной' again functions as an adjective, modifying 'зарядное устройство', specifying its portability suitable for trips.
Для поездок я предпочитаю иметь портативной зарядное устройство.
For trips, I prefer to have a portable charger.
Here, 'портативной' is used as an adjective to describe the noun 'компьютер', indicating that the computer is portable.