Ed Pegg, math funers:
Robert G. Wilson V somehow determined that the prime number in the subject divides Googolplex+1.
I verified this ... but I don't know what cleverness he used to find it.
I suspect he used legendary cleverness... or should I say "Legendre." Numbers of the form a^n+b^n have two kinds of factors. - The algebraic factors are a^m+b^m, where M is N divided by an odd number. - The primitive factors are those primes which divide a^n+b^n, but not any algebraic factor. Legendre showed that they are all of the form k*n+1, for some K. In our case, a=10, b=1, and n=google: For each odd factor of google (each small power of 5), the cofactor C is 2^100*5^d for some D. 10^C+1 is an algebraic factor of 10^google+1, and its primitive prime factors are k*(2^100*5^d)+1. Each such primitive factor also factors 10^google+1. One can check values of D from 0 upwards, and values of K from 1 upwards. Perhaps that's what Dr. Wilson did. It happens that d=6, k=16 yields Robert's prime factor. -- Don Reble djr@nk.ca