## Task B-2.5.

What is the last digit of the sum of all positive divisors of the number $105$?
## Solution.

$$
105=3 \cdot 5 \cdot 7
$$

The divisors of 105 are 1, 3, 5, 7, 15, 21, 35, 105.

The sum of the divisors is 192. The last digit of the sum is 2.