1. Four: 20140301 and 20140303, 20140829 and 20140831, 20140907 and 20140909, 20141201 and 20141203
2. 20160401 and 20160403
3. 20170831 and 20170901
4. 20170831, 20170901, 20170903
5. 20800529, 20800531, 20800601, 20800603, 20800607
6. 30830131, 30830201, 30830203, 30830207, 30830209
7. October 7th. This comes from M2203, whose full 2^p1 value taken as ...yyyyymmdd is a 660 digit year with 1007 as mmdd. Some fun trivia: this prime was discovered on its "date" (just the wrong year), October 7th, 1952. The other Mersenne prime days are from M4423 (0607) and M37156667 (0927). Neither of them share the property of being found on their "day". And if you try to take the p as the date instead of 2^p1, no Mersenne prime days are known. We'll probably discover one some day.
8. 1111111111111111111 (111 trillion years from now)
Last fiddled with by MiniGeek on 20141201 at 16:36
