program DigitFactorialNumbers;
const
MaxDigit = 9;
function Factorial(n: Integer): LongInt;
var
i, fact: LongInt;
begin
fact := 1;
for i := 2 to n do
fact := fact * i;
Factorial := fact;
end;
procedure FindDigitFactorialNumbers;
var
factorials: array[0..MaxDigit] of LongInt;
i, num, temp, digit, sum, upperLimit: LongInt;
begin
// Precompute factorials of digits 0-9
for i := 0 to MaxDigit do
factorials[i] := Factorial(i);
upperLimit := 7 * factorials[9]; // 7 * 9! is a safe upper bound
for num := 10 to upperLimit do
begin
sum := 0;
temp := num;
while temp > 0 do
begin
digit := temp mod 10;
sum := sum + factorials[digit];
temp := temp div 10;
end;
if sum = num then
writeln(num, ' is a digit factorial number.');
end;
end;
begin
FindDigitFactorialNumbers;
end.
(*
run:
145 is a digit factorial number.
40585 is a digit factorial number.
*)
