A number is divisible by 8 when its last three digits form a number divisible by 8. Here the last three digits are 512, and \(512 \div 8 = 64\), so the divisibility-by-8 condition is satisfied for every value of y.

A number is divisible by 9 when the sum of its digits is divisible by 9. The digit sum is \(6 + y + 5 + 1 + 2 = 14 + y\).

For \(14 + y\) to be a multiple of 9, the next multiple after 14 is 18, so \(14 + y = 18\), giving \(y = 4\).

Hence, the digit y is 4.