81873...40415 (29-digits)

This number is a composite.

                                             818738425 7421346600 6829740415

G. L. Honaker, Jr. conjectures that 2^2*3^3*19^19*11251^11251*2980024297506569894680811251^2980024297506569894680811251+1 is prime. Note that 2^2+1, 2^2*3^3+1, 2^2*3^3*19^19+1, and 2^2*3^3*19^19*11251^11251+1, are all proven primes. (He offers a free Prime Curios! T-Shirt to the first person that can prove or disprove the primality of this 81873842574213466006829740415-digit number.)