562949953421311

This number is a composite.

                                                            56294 9953421311

The largest known semiprime of the form 2^n^2-1. Since 2^n^2-1 will always divisible by 2^n-1, then it is clear that 2^n^2-1 could be a semiprime if and only if 2^n-1 is prime. The next semiprime of the form 2^n^2-1 will have more than 100 million digits, where the smallest unknown candidate is 2^19937^2-1. [Tolgede]