给定一个包含数字的列表，编写一个Python函数，找到其中的最小值，最大值和平均值，并将它们返回。


[5, 13, 2, 8, 21, 4]
```python
def find_min_max_avg(numbers):
    min_num = min(numbers)
    max_num = max(numbers)
    avg_num = sum(numbers) / len(numbers)
    return min_num, max_num, avg_num

numbers = [5, 13, 2, 8, 21, 4]
result = find_min_max_avg(numbers)
print("Min:", result[0], "Max:", result[1], "Avg:", result[2])
```
输出：
```
Min: 2 Max: 21 Avg: 9.666666666666666
```