splitting a string into an array of 3 character from behind [on hold]

I'm looking to split a numeric random string like "12345567" into the array ["12","345","567"] as simply as possible. basically changing a number into a human readable number array with splits at thousands,million, billions, etc..

my previous solution cuts it from the front rather than back

"'12345567".to_s.scan(/.{1,#{3}}/)
#> ["123","455","67"]