c# and stack over flow

Question

i got two question why i get stack overflow and why after changing area radius does not change
class Program
{
static void Main(string[] args)
{
Circle a = new Circle(3,3,4);//R=3
Circle b = new Circle(5, 6, 3);//R =5
Console.WriteLine(a.CompareTwoCircles(b));// return -1 a<b
a.Radius = 6;
Console.WriteLine(a.CompareTwoCircles(b));//return 1 a >b
//------------------------------------
Console.WriteLine(a.Area);
Console.WriteLine(a.circumference);
a.Area = 153.94;
Console.WriteLine(a.Radius); //7 expected

}
}

class Circle
{
private Cartesian centerOfcircle;
public double Radius
{
set { this.Radius = Math.Abs(value); }
get { return this.Radius; }
}
public double Area{
get { return Math.PI * (Radius * Radius); }
set
{
this.Radius = Math.Abs(Math.Sqrt(this.Area / Math.PI));
}
}
public double circumference {

get { return 2 * Math.PI * Radius; }
set
{
this.Radius = Math.Abs(this.circumference / Math.PI / 2);

}
}

public Circle(double radius , double x , double y) {
this.centerOfcircle = new Cartesian(x, y);
this.Radius = Math.Abs(radius);
}
public int CompareTwoCircles(Circle input)
{
if (Radius > input.Radius) return 1;
else if (Radius == input.Radius) return 0;
else return -1;

}
}