------
## 最终结论
```python
def iscube(a):
    if a >= 0:
        cube_root = round(a ** (1/3))
        return cube_root ** 3 == a
    else:
        abs_a = abs(a)
        cube_root = round(abs_a ** (1/3))
        return cube_root ** 3 == abs_a
```