To find the sum of the interior angles of a polygon, you can use the formula:
\[ \text{Sum of interior angles} = (n - 2) \times 180 \]
where \( n \) is the number of sides in the polygon.
For a hendecagon, which has 11 sides:
\[ \text{Sum of interior angles} = (11 - 2) \times 180 \] \[ = 9 \times 180 \] \[ = 1620 \]
Thus, the sum of the interior angles of a hendecagon is \( \boxed{1620} \) degrees.