Plaintext and ciphertext block sizes
With an alphabet of 27 characters, the maximum number of characters that can fit into one plaintext block is equal to the largest integer less than or equal to $\text{log}(n) / \text{log}(27)$:

$$\bigg\lfloor\frac{\text{log}(59768553302699443)}{\text{log(27)}}\bigg\rfloor = 11$$

On the other hand, assuming the ciphertext is represented as a string of characters in the same alphabet, the minimum ciphertext length will be 12. This is because it will have to accommodate a maximum value of $n$, which is greater than $27^{11}$.