pow()

public BigInteger pow( int exp )

Returns a BigInteger whose value is the integer raised to the power exp. Throws an ArithmeticException if exp is negative.

Notice that the exponent is an int, not a BigInteger. An int can be as large as two billion and it is unlikely you will need an exponent larger than this.

Of course, an integer raised to an integer power results in an integer, so BigInteger is the appropriate data type.