Imports System
' A number is a twisted prime number if the reverse of the number is also a prime number
Public Class Program
Public Shared Function reverseNumber(ByVal n As Integer) As Integer
Dim reminder As Integer, reverse As Integer = 0
While n <> 0
reminder = n Mod 10
reverse = reverse * 10 + reminder
n = n \ 10 ' \ not /
End While
Return reverse
End Function
Public Shared Function isPrime(ByVal n As Integer) As Boolean
If n < 2 OrElse (n Mod 2 = 0 AndAlso n <> 2) Then
Return False
End If
Dim count As Integer = CInt(Math.Floor(Math.Sqrt(n)))
For i As Integer = 3 To count Step 2
If n Mod i = 0 Then
Return False
End If
Next
Return True
End Function
Public Shared Sub Main()
Dim n As Integer = 79
Dim reverse_n As Integer = reverseNumber(n)
If isPrime(n) AndAlso isPrime(reverse_n) Then
Console.Write("Twisted prime number")
Else
Console.Write("Not twisted prime number")
End If
End Sub
End Class
' run:
'
' Twisted prime number
'
