Laxey of the Isle of Man, was built in 1854 to pump water from the Laxey mine shafts. Now a tourist attraction, it remains the largest working waterwheel in the world. Designed by Robert Casement, it is in diameter and wide. It revolves at about 3 rpm. The mines employed over 600 miners at their peak, producing lead, copper, silver and zinc, until they closed in 1929. The Wheel was owned by Edwin Kneale from 1939 to 1965; he saved it from being dismantled and ran it as a tourist attraction, before passing it on to the Manx nation, with the
Largest known prime number the progression of the largest known prime number in ascending order. Here M = 2 − 1 is the Mersenne number with exponent "n". The longest record-holder known was M = 524,287, which was the largest known prime for 144 years. No records are known before 1456. GIMPS found the fourteen latest records (all of them Mersenne primes) on ordinary computers operated by participants around the world. A list of the 5,000 largest known primes is maintained by Chris K. Caldwell, of which the twenty largest are listed below. Largest known prime number The largest known prime number () is