If it is possible to make only one such number with the first, the fourth and the sixth digits of the number 531697, which is the perfect square of a two-digit even number, which of the following will be the second digit of the two-digit even number. If no such number can be made, give'@' as the answer and if more than one such numbers can be made, give '©' as the answer.
5 3 1 6 9 7
I I I
5 6 7
Perfect square = 576, Square root = `sqrt576` = 24
Hence, second digit = 4