/4[0-9]{3}[ \-,]?(?:(?:[0-9]{3}[ \-,]?[0-9]{3}[ \-,]?[0-9]{3})|(?:[0-9]{4}[ \-,]?[0-9]{4}[ \-,]?[0-9]{4}))/
#+ number only field starts with 4 - 13 or 16 digits
4024616786980
4325795326593156
#+ number string
<sometag1>somedata</sometag1><sometag2><num>4024616786980</num>
<sometag1>somedata</sometag1><sometag2><num>4325795326593156</num>
#+ with spaces
<sometag1>somedata</sometag1><sometag2><num>4024 616 786 980</num>
<sometag1>somedata</sometag1><sometag2><num> 4325 7953 2659 3156</num>
#+ with dash
<sometag1>somedata</sometag1><sometag2><num>4024-616-786-980</num>
<sometag1>somedata</sometag1><sometag2><num>4325-7953-2659-3156</num>
#+ with comma
<sometag1>somedata</sometag1><sometag2><num>4024,616,786,980</num>
<sometag1>somedata</sometag1><sometag2><num>4325,7953,2659,3156</num>
#+ bigger numbers
<sometag1>somedata</sometag1><sometag2><num>402461678698065768745</num>
<sometag1>somedata</sometag1><sometag2><num>432579532659315634646874</num>
#+ bigger numbers with space
<sometag1>somedata</sometag1><sometag2><num>3449 9003004 284024 616 786 980566</num>
<sometag1>somedata</sometag1><sometag2><num>3449 9003004 2432579532659315666</num>
#- SHOULD NOT MATCH with other starting numbers
21342454657764
37592951984335
39152870324798
<sometag1>somedata</sometag1><sometag2><num>3532579532659315665 566</num>
