
theorem Th495:
Sum digits(1660,10) = 13
proof
  thus Sum digits(1660,10) = Sum <%0,6,6%>+Sum <%1%> by Th494,AFINSQ_2:55
  .= Sum <%0,6%> + Sum <%6%> + Sum <%1%> by AFINSQ_2:55
  .= (0 + 6) + Sum <%6%> + Sum <%1%> by AFINSQ_2:54
  .= (0 + 6 + 6) + Sum <%1%> by AFINSQ_2:53
  .= 12 + 1 by AFINSQ_2:53
  .= 13;
end;
