BigInteger is in an immutable object, so you need to assign the results of any mathematical operation, to a new BigInteger instance.
Addition: 10 + 10 = 20
BigInteger value1 = new BigInteger("10");
BigInteger value2 = new BigInteger("10");
BigInteger sum = value1.add(value2);
System.out.println(sum);
output: 20
Substraction: 10 - 9 = 1
BigInteger value1 = new BigInteger("10");
BigInteger value2 = new BigInteger("9");
BigInteger sub = value1.subtract(value2);
System.out.println(sub);
output: 1
Division: 10 / 5 = 2
BigInteger value1 = new BigInteger("10");
BigInteger value2 = new BigInteger("5");
BigInteger div = value1.divide(value2);
System.out.println(div);
output: 2
Division: 17/4 = 4
BigInteger value1 = new BigInteger("17");
BigInteger value2 = new BigInteger("4");
BigInteger div = value1.divide(value2);
System.out.println(div);
output: 4
Multiplication: 10 * 5 = 50
BigInteger value1 = new BigInteger("10");
BigInteger value2 = new BigInteger("5");
BigInteger mul = value1.multiply(value2);
System.out.println(mul);
output: 50
Power: 10 ^ 3 = 1000
BigInteger value1 = new BigInteger("10");
BigInteger power = value1.pow(3);
System.out.println(power);
output: 1000
Remainder: 10 % 6 = 4