The factors of the number 644,611,520 are: 1, 2, 4, 5, 7, 8, 10, 14, 16, 20, 28, 31, 32, 35, 40, 56, 62, 64, 70, 80, 112, 124, 140, 155, 160, 217, 224, 248, 280, 310, 320, 434, 448, 496, 560, 620, 868, 992, 1085, 1120, 1240, 1736, 1984, 2170, 2240, 2480, 3472, 4340, 4960, 6944, 8680, 9283, 9920, 13888, 17360, 18566, 34720, 37132, 46415, 64981, 69440, 74264, 92830, 129962, 148528, 185660, 259924, 287773, 297056, 324905, 371320, 519848, 575546, 594112, 649810, 742640, 1039696, 1151092, 1299620, 1438865, 1485280, 2014411, 2079392, 2302184, 2599240, 2877730, 2970560, 4028822, 4158784, 4604368, 5198480, 5755460, 8057644, 9208736, 10072055, 10396960, 11510920, 16115288, 18417472, 20144110, 20793920, 23021840, 32230576, 40288220, 46043680, 64461152, 80576440, 92087360, 128922304, 161152880, 322305760, 644611520.
If you add them up, you will get the total of 1,811,048,448.