The numbers less than 696 and are squares of certain numbers are 676, 625.The least number that should be subtracted from 696 to make it perfect square = 696 - 676 = 20.
Let the ten's digit be x and unit's digit be y. Then, number 10x + y.Number obtained by interchanging the digits = 10y + x.(10x + y) + (10y + x) = 11(x + y)which is divisible by 11.
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