go =>
  foreach(N in [627615,39390,588225,393900588225,
                58142718981673030403681039458302204471300738980834668522257090844071443085937])
    [Sum,Persistence] = digital_root(N),
    printf("%w har addititive persistence %d and digital root of %d\n", N,Persistence,Sum)
  end,
  nl.

%
% (Reduced) digit sum (digital root) of a number
%
digital_root(N) = [Sum,Persistence], integer(N)  =>
   Sum = N,
   Persistence = 0,
   while(Sum > 9)
     Sum := sum([I.to_integer() : I in Sum.to_string()]),
     Persistence := Persistence + 1
   end.