Is 2 to the 67 power - 1 a prime?

Yes

or no. 2 to the 67 power minus 1 is 147,573,952,589,676,412,927.

761,838,257,287

x 193,707,721

____________

147,573,952,589,676,412,927.

Therefore 2 to the 67th power minus 1 is not a Prime number. This is according to mathematician Frank Nelson Cole.