Unknown apps/processes with number only are shown in the battery screen There is a mysterious app, 99070 that is consuming power on my Nexus 5X. Any idea how I determine what it is?

There is no option to stop or uninstall it. My phone is a Nexus 5X running stock Android 6.0.
Possibly right answer:

It's a sandboxed process from a removed app.

For such a number over 99000, it is the Unix UID for an isolated sandbox process (u0_i70).

In Android's UID system, called "AID". Android allocated 1000 special UIDs for isolated sanbox processes, 99000-99999. Some apps use that for security reasons, like Chrome (Incognito mode).