This is a puzzle proposed by D. R. Kaprekar in year1984.
In the year 1949, a man turned 67. His four sons turned 37, 31, 29, 23. All the five reached prime age in a prime year. It was the golden year for the family. When was or will be their next golden year ?
(Prob 8-3-1, Function, Col 8, Dept of Mathematics, Monash University, Claighton, Victoria, 3168, July 84, pg. 28)