Paste the string in a cell, open search and replace dialog (ctrl + f) extended search option mark regular expression search for ([\s,0-9])([^0-9\s])+ and replace it with \$1
now you get a list like 24991 24991 24991 24991 24994 24994 24995 24995 24996 24996 24996
to replace mutliple withespaces (e.g. ibetween 24991 24994) search for \s+ and replace it with , to get the comma between. ;-)