Square

Square of a number x1x2x3...xr−1xr.
Take a number 26374.
Express it as x1x2x3x4x5.
Then square of x1x2x3x4x5 is equal to

In this manner you can find out square of any number.
Some more examples.
Find square of 45128 as shown below

The above series is the expansion of the basic postulates, 

 (xy)^2 = x(x+1)y^2 + 20x(y-5).

Look at the following examples as shown below.