83. Even or odd sum of all natural numbers from 1 to 17?
$\triangle$ Out of 17 natural numbers, 8 are even:

$$
2,4,6,8,10,12,14,16 \text{, }
$$

the remaining 9 are odd. The sum of all these even numbers is even (property 3), the sum of the odd numbers is odd (property 5). Therefore, the sum of all 17 numbers is odd as it is the sum of an even and an odd number (property 4).

Answer: odd.