Imports System
Module Program
' Function to check if a number is prime
Function IsPrime(n As Integer) As Boolean
If n < 2 Then Return False
If n Mod 2 = 0 Then Return n = 2
Dim limit As Integer = CInt(Math.Sqrt(n))
For i As Integer = 3 To limit Step 2
If n Mod i = 0 Then Return False
Next
Return True
End Function
' Function to check if all digits are unique
Function HasUniqueDigits(n As Integer) As Boolean
Dim seen(9) As Boolean ' track digits 0–9
While n > 0
Dim d As Integer = n Mod 10
If seen(d) Then Return False ' duplicate found
seen(d) = True
n \= 10
End While
Return True
End Function
Sub Main()
For num As Integer = 1000 To 9999
If IsPrime(num) AndAlso HasUniqueDigits(num) Then
Console.WriteLine($"First 4-digit prime with all unique digits: {num}")
Return ' stop after finding the first one
End If
Next
Console.WriteLine("No such number found.")
End Sub
End Module
' run:
'
' First 4-digit prime with all unique digits: 1039
'
