Sixty-five million sound like a big deal by any standard. That's the size of the improvement that an online army of collaborating mathematicians has already made to a groundbreaking proof involving pairs of prime numbers,which was first announced just a few weeks ago. Though the improvement is big, mathematically speaking it amounts to a technicality. Still, the achievement showcases a new way of doing mathematics online. Since the proof appeared, mathematicians from across the world have been locked in an addictive race to tighten it up. The work relates to a longstanding problem called the twin prime number can only be divided by 1 and itself, and twin primes are those just two numbers apart,like 3 and 5,or 29 and 31.The conjecture, put forward in 1849, says there are an infinite number of these pairs,but no one has managed to prove or disprove it.