Imports System
Imports System.Collections.Generic
Module DigitFactorialModule
' Example: 145 = 1! + 4! + 5! = 1 + 24 + 120 = 145
' Function to compute the factorial of a number
Function Factorial(n As Integer) As Integer
Dim fact As Integer = 1
For i As Integer = 2 To n
fact *= i
Next
Return fact
End Function
' Function to find all numbers equal to the sum of the factorials of their digits
Sub FindDigitFactorialNumbers()
' Precompute factorials of digits 0-9
Dim factorials As New List(Of Integer)(10)
For i As Integer = 0 To 9
factorials.Add(Factorial(i))
Next
' Define an upper limit (7 * 9! is a safe limit for this problem)
Dim upperLimit As Integer = 7 * factorials(9)
' Iterate through all numbers and check the condition
For num As Integer = 10 To upperLimit
Dim sum As Integer = 0
Dim temp As Integer = num
' Calculate the sum of factorials of digits
While temp > 0
Dim digit As Integer = temp Mod 10
sum += factorials(digit)
temp \= 10
End While
' Check if the number equals the sum of the factorials of its digits
If sum = num Then
Console.WriteLine($"{num} is a digit factorial number.")
End If
Next
End Sub
Sub Main()
FindDigitFactorialNumbers()
End Sub
End Module
' run:
'
' 145 is a digit factorial number.
' 40585 is a digit factorial number.
'
