using System;

using System.Text.RegularExpressions;   

​

public class Program

{

    public static void Main()

    {

        var regex = @"^(?<number>[АВЕКМНОРСТУХABEKMHOPCTYX]{1}\d{3}[АВЕКМНОРСТУХABEKMHOPCTYX]{2})(?<region>\d{2,3}){2}$";

        var match = Regex.Match("X272YB136136",regex);

        Console.Write(match.Success);

    }

}