Let,

Unit's place digit be x

Ten's place digit be ( x + 1 )

Number = 10( x + 1 ) + x

Given, product of the number and the number obtained by reversing the digits is 252.

Original number = 10( x + 1 ) + x

Number when digit are reversed = 10x + ( x + 1 )

Product = [ [10( x + 1 ) + x ] [ 10x + ( x + 1 ) ]

= > 252 = [ 10x + 10 + x ] [ 10x + x + 1 ]

= > 252 = [ 11x + 10 ] [ 11x + 1 ]

= > 252 = 121x^2 + 11x + 110x + 10

= > 252 = 121x^2 + 121x + 10

= > 121x^2 + 121x + 10 - 252 = 0

= > 121x^2 + 121x - 242 = 0

= > 121( x^2 + x - 2 ) = 0

= > x^2 + x - 2 = 0

= > x^2 + ( 2 - 1 ) x - 2 = 0

= > x^2 + 2x - x - 2 = 0

= > x( x + 2 ) - ( x + 2 ) = 0

= > ( x + 2 ) ( x - 1 ) = 0

= > x = - 2 or x = 1

It is given that the required number is a natural number, so x can't be equal to - 2. Therefore, x = 1 .

Then,

Unit's place of the number = x

Unit's place of the number = 1

Ten's place of the number = x + 1

Ten's place of the number = 1 + 1

Ten's place of the number = 2

Therefore, required natural number = xy = 21

Required number = 21 .