35. NUMB3RS. The RSA Factoring Challenge, which ended in 2007, challenged computational mathematicians to factor extremely large numbers that were the product of two prime numbers. The largest number successfully factored in this challenge was RSA-640, which has 193 decimal digits and carried a prize of $\$ 20,000$. The next challenge number carried prize of $\$ 30,000$, and contains $N$ decimal digits. Your task is to submit a guess for $N$. Only the team(s) that have the closest guess(es) receives points. If $k$ teams all have the closest guesses, then each of them receives $\left\lceil\frac{20}{k}\right\rceil$ points.
Answer: 212 For more information, see the Wikipedia entry at http://en.wikipedia.org/wiki/ RSA_Factoring_Challenge.
RSA-640 was factored in November 2005, and the effort took approximately $302.2 \mathrm{GHz}$-Opteron-CPU years over five months of calendar time.