Find the odd number / letters / word from the given alternative:

15
63
143
195 E. 257

The odd number in the given list is $\boxed{195}$. All other numbers are perfect squares.

A perfect square is a number that can be obtained by squaring an integer. In other words, it is a number of the form $n^2$, where $n$ is an integer.

The numbers 15, 63, 143, and 257 are all perfect squares. They can be obtained by squaring the integers 3, 7, 11, and 16, respectively.

195 is not a perfect square. It cannot be obtained by squaring any integer.