Answer:
193664 sheets of paper.
Explanation:
We know that the pressure is defined as

In words, the applied force divided by the area of application. The area of a single sheet of paper is

The force exerted by a single sheet of paper is its weight, given by teh expression:

(Where m is the mass of a single sheet and g is the acceleration due to gravity on earth)
And, for
sheets of paper, the total weight is:

Now, substituting this in the definition of pressure and solving for
, we get:

Finally, plugging in the known values, we can compute
:

This means that there must be 193664 sheets stacked to produce a pressure equal to atmospheric pressure.