Meaning of bitwise and(&) of a positive and negative number?

Question

Can anyone help what n&-n means?? And what is the significance of it.

Answer 1

I would add a self-explanatory example to the Mark Randsom's wonderful exposition.

010010000 | +144 ~
----------|-------
101101111 | -145 +
        1 |
----------|-------
101110000 | -144 

101110000 | -144 & 
010010000 | +144
----------|-------
000010000 |   16`