Why can I parse invalid values to an Enum in .NET?

Why is this even possible? Is it a bug?

using System;

public class InvalidEnumParse
{
    public enum Number
    {
        One,
        Two,
        Three,
        Four
    }

    public static void Main()
    {
        string input = "761";
        Number number = (Number)Enum.Parse(typeof(Number), input);
        Console.WriteLine(number); //outputs 761
    }
}