1 | initial version |

2 | No.2 Revision |

~~You ~~To extract the divisors less than 10, you can do this:

```
sage: k = 720
sage: sum(d for d in k.divisors() if d < 10)
```

See this tutorial.

The error you got is probably because of the following:

If you defined `d`

as

```
sage: d = divisors(k)
```

Then `d`

is a list. You can extract element number `i`

of `d`

as `d[i]`

, but you cannot do `d(i)`

which would be "calling the function `d`

with argument `i`

". Sage tells you `d`

is not "callable".

If you want to sum the first 10 divisors, do:

```
sage: sum(d[i] for i in range(10))
```

or

```
sage: sum(d[:10])
```

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