Analysis:
(Solution 1) $2015=5 \times 13 \times 31$
The sum of all divisors of 2015 is $\left(5^{0}+5^{1}\right) \times\left(13^{0}+13^{1}\right) \times\left(31^{0}+31^{1}\right)=6 \times 14 \times 32=2688$
The sum of all non-trivial divisors of 2015 is $2688-1-2015=672$
(Solution 2) Since the number is relatively small, we can directly list all the divisors of 2015
$$
2015=1 \times 2015=5 \times 403=13 \times 155=31 \times 65
$$
The sum of all non-trivial divisors of 2015 is $5+403+13+155+31+65=672$
【Question 3】 Divisors of 2015 are called factors of 2015. 1 and 2015 obviously divide 2015, and are called trivial factors of 2015. In addition to the trivial factors, 2015 has some non-trivial factors. Therefore, the sum of all non-trivial factors of 2015 is $\qquad$ .