How to add parentheses between numbers? I know how to add dashes, are they doing the same way?

Question

how to add parentheses between numbers? I know how to add dashes, are they doing the same way? like 123456789 to (123)456789 in R programming?

Answer 1

sub("(\\d{3})", "(\\1)", 123456789)
[1] "(123)456789"