What is the largest Possible Stack size?

[NewMexico]

What is the largest number possible to stack in one square?

Does it vary by Map?

[MoB Deadly]

There is no limit I believe. However if you try to attack with extremely large stacks I think it causes the browser to crash. Here is an example of 3M+ troops on one region.

Game 7961282

[Metsfanmax]

Well, there will be an inherent limit associated with how much can be represented in memory by a 32 bit integer (about 2 billion for signed integers, and 4 billion for unsigned). If the server uses 64 bit integers (unlikely), then the limit is effectively infinite.