You could do this with a 32 bit number:

var hexValue:int = 0x800206A0

var unsignedValue:Number = (hexValue & 0x7FFFFFFF);
// unsignedValue now equals 132,768

var signedValue:Number = unsignedValue;

// if the signed flag is set, flip the value
if ((hexValue >> 31) == 1) {
signedValue = unsignedValue – 0×80000000;
}