In reply to @standupmaths
@standupmaths best you can do is 379. 379,397,739,9638 prime but 793, 973 not. Answers with repeated digits: 113, 199
In reply to @christianp
@christianp @standupmaths well of course I meant 963 not 9638
In reply to @christianp
@christianp and I should read my computer better: 149 also has 4 prime permutations