Show that no proper divisor of a perfect number is perfect.

proof. let n be perfect, and let $\displaystyle d_{1},d_{2},...,d_{r} $ be divisors of n. Now, $\displaystyle O(n) = 2n = 1 + d_{1},d_{2},...,d_{r} $.

Now, what should I do to get O(d) not equal to 2d for all ds?