3520

There were 3520 days from 09/11/01 until 05/02/11 (the date Bin Laden ימ"ש was killed, local time).

According to gezageza, one of the verses with the gematria of 3520 is from Mishlei 10:27:

יִרְאַת יְהוָה, תּוֹסִיף יָמִים;    וּשְׁנוֹת רְשָׁעִים תִּקְצֹרְנָה.

The fear of the LORD prolongeth days; but the years of the wicked shall be shortened.