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This is not a problem that software can compute. Assuming you do not have to control impedance, the maximum number of layers is dictated by the minimum dielectric thickness that can be achieved by the board fab.
Typically, today's advanced technology for board fab can handle down to about 0.002in for dielectric. MIL SPEC says minimum is 0.0035in. That means, in theory, you can acheive 24 layers in 0.065in thickness for a non-MILSPEC board. For a MILSPEC board, you are forced to go thicker.
The answer to your question can only come from your board fab. They alone can tell you if they have the capability to use minimum dielectric thicknesses with your particular stackup and hold the overall board to 0.065in.