The ages of the 36 executives are organized as follows:
\[
\text{Ages} = [29, 30, 33, 33, 34, 34, 36, 37, 37, 37, 40, 41, 41, 41, 42, 43, 43, 43, 45, 45, 50, 52, 52, 53, 58, 60, 60, 61, 61, 61, 62, 63, 63, 64, 66, 66]
\]
To find the percentile corresponding to an age of \(42\) years, we count the number of executives whose ages are less than or equal to \(42\):
- Count of ages \( \leq 42 \): \( 15 \)
- Total number of executives: \( 36 \)
The percentile is calculated using the formula:
\[
\text{Percentile} = \left( \frac{\text{Count of values} \leq 42}{\text{Total count}} \right) \times 100
\]
Substituting the values:
\[
\text{Percentile} = \left( \frac{15}{36} \right) \times 100 \approx 41.67
\]
Rounding to the nearest integer gives us \(42\).
The percentile of \(42\) years old is
\(\boxed{42}\).