Suppose I have the following dataframe

```
import pandas as pd
df = pd.DataFrame( {3: {0: 'Total shareholders’ equity, beginning balances', 1: 'Total shareholders’ equity, beginning balances', 2: 'Total shareholders’ equity, beginning balances', 3: '$', 4: '90488', 9: '$', 10: '107147', 15: '$', 16: '134047'}} )

```

As you can see that index 4, 10, 16 are numbers. How can I extract these numbers automatically.

Note: As you can see this column contain strings as well as numbers but those numbers are read as strings.