8128

This number is a composite.

The largest perfect number whose index is equal to the number of digits. [Pol]

The largest perfect number of the form 2^(p-1)*(2^p-1), where the prime number p and the perfect number both have the same index. [Pol]

In addition to being a perfect number, its reverse (8218) is the 8128th positive integer that is non-square. [Gaydos]