If a number 2x1y6z is divisible by 9, then the least possible value of x + y + z is:

We know that a number N is divisible by 9 if the sum of its digits is divisible by 9.

Here, sum of the known digits of 2x1y6z = 2 + x + 1 + y + 6 + z = 9 + x + y + z

Let x + y + z = 0, which is the least possible value.

Then, the sum of the known digits of 2x1y6z = 9 + 0 = 9, which is divisible by 9.

Therefore, the least possible value of (x + y + z) is 0.