Even a desktop computer would be able to serve in that capacity although, it depends largely on the loads of work you subject the device to. Any device would work as exchanges are basically online and don't need any much space to work except for browsers that can access them sites. Wallets just need a few kilobytes to be installed and run successfully, although how safe it is depends largely on what and what you install or choose to click on your device.
Keep a device very functional would add you in working a exchange and so, you might as well want to ensure a proper well being of your device by updating antivirus programs, have well enough ram & rom, avoid over hitting of your device, close tabs that aren't in use and general stuff like that.