EntityId
From Nomad DB
Every Entity that exists in the game world has a unique Entity ID. It is a 64-bit unsigned integer, represented in Lua as a string. This also applies to multiple instances of a single entity. Additionally, Entity IDs are dynamic, meaning an entity that is always being spawned will have a different ID each time the game is run. An exception to this are entities inside WLUs as they have pre-defined IDs.
Example
15738498423673481953
Invalid Entity Id
Some functions that return an Entity ID might return one that is invalid. An Entity ID can always be compared against GetInvalidEntityId to find out whether it is valid or not.