The Sierpinski prime problem has been around for about 50 years. The lowest known Sierpinski number is 78,557 and the quest is on to find the smallest. After decades of effort, it had been narrowed down to six possible candidates: 10223, 21181, 22699, 24737, 55459 and 67607.
It's one of those "pure math" problems that sounds tantalizing simple to calculate, but requires immense computational effort.
After the announcement last month of the 7th largest known prime number, you can now strike 10223 off the list.
https://www.newscientist.com/article/2113283-crowdsourced-prime-number-could-help-solve-a-50-year-old-problem/
