17 × 59 = 10003

you’ve got an extra zero in there, and you forgot the 1, but the rest of your divisors match my crude brute-force approach:

>>> n=31521281
>>> d = [ x for x in range(1,n//2+1) if not n%x ]
>>> d
[1, 11, 17, 59, 187, 649, 1003, 2857, 11033, 31427, 48569, 168563, 534259, 1854193, 2865571]
>>> yours=list(map(int,"11+17+59+2857+11033+534259+1854193+2865571+168563+48569+10003+31427+649+187".split("+")))
>>> set(yours) - set(d)
{10003}
>>> set(d) - set(yours)
{1, 1003}
>>> sum(d)
5518399

same conclusion though: 5518399 also ≠ 31521281

>>> isperfect = lambda n: n == sum(x for x in range(1,n//2+1) if not n%x)
>>> [n for n in range(1, 10000) if isperfect(n)]
[6, 28, 496, 8128]