code: private final int getLowestSetBit() {
          if (intLen == 0)
              return -1;
          int j, b;
          for (j=intLen-1; (j > 0) && (value[j+offset] == 0); j--)
              ;
          b = value[j+offset];
          if (b == 0)
              return -1;
          return ((intLen-1-j)<<5) + Integer.numberOfTrailingZeros(b);
      }
docs: Return the index of the lowest set bit in this MutableBigInteger. If the
  magnitude of this MutableBigInteger is zero, -1 is returned.