knoppix@Microknoppix:~$ perl -E '
$num = q{17403 4893 18345-973409};
say $num;
push @seps, [ $1, $-[ 0 ] ] while $num =~ m{(\D)}g;
$num =~ s{\D}{}g;
$maskLen = length( $num ) - 10;
substr $num, 6, $maskLen, q{X} x $maskLen;
substr $num, $_->[ 1 ], 0, $_->[ 0 ] for  @seps;
say $num;'
17403 4893 18345-973409
17403 4XXX XXXXX-XX3409
knoppix@Microknoppix:~$