Native format is BLEND file, this file contains textures, materials and HDRI background packed into blend file, modifiers are not applied yet so you can play with them to make some modifications to the model like subdivide it more or less depending on what you need.
Polycount made with modifiers not applied.
Other formats are:
OBJ MAX FBX STL
Tested into 3DS MAX 2015 and opens with no problem.