Find the least value that must be given

Given, 91876a2 is divisible by 8.

Since, we know that, if a number is divisible by 8, then the number formed by last 3 digits is divisible by 8.

So, 6a2 is divisible by 8.

Here, a can take values from 0 to 9.

For a = 0, 602 is not divisible by 8.

For a = 1, 612, which is not divisible by 8.

For a = 3, 632 is divisible by 8.

Hence, the minimum value of a is 3 to make 91876a2 divisible by 8.