Which least number should be added to 1000 so that 53 divides the sum exactly?

To find the least number to be added to 1000 so that the sum is exactly divisible by 53, we divide 1000 by 53 and find the remainder.

$\begin{array}{l} \phantom{x^2 }{\quad 18} \ 53\overline{\smash{\big)}1000} \ \phantom{x}\phantom{(}\underline{-53} \ \phantom{{x^2 }()} 470 \ \phantom{{x}(}\underline{-424} \ \phantom{{x^2 (()}} 46 \ \end{array}$

The remainder when 1000 is divided by 53 is 46.

The least number to be added to 1000 = 53 - 46 = 7.

Therefore, 1000 + 7 = 1007, which is exactly divisible by 53.

Hence, the least number to be added to 1000 is 7.