How do I, in as few operations as possible, round off a number in this way:

133, is (2^7) + (2^4) + (2^1)

It must become 127: (2^6) + (2^5) + (2^4) + (2^3) + (2^2) + (2^1)


And if for instance, the given number was 250, it would round to 255

Trivial?