A six digit number has the maximum number of possibilities of perfect square as given below
1) First digit is a perfect square
2) Second digit is a perfect square
3) Third digit is a perfect square
4) Number formed by first and second digit in order is perfect square.
5) Number formed by third and fourth digit in order is a perfect square.
6) Number formed by fifth and sixth digit in order is a perfect square.
7) Number formed by last 3 digit in order is a perfect square.
Here sixth digit means the units place.
All the digits in the number are different and non-zero.
The product of all the six digit will be
Perfect square single digits are 1, 4, 9
Two digit no by using 1, 4, 9 is only 49
So first three no will be 491 now third and fourth digit number is perfect square so it will be 16 and last two digit set will only be 25 because no integer can be revised so no is 491625