The factors of the number 6,421,968 are: 1, 2, 3, 4, 6, 7, 8, 9, 12, 14, 16, 18, 21, 23, 24, 28, 36, 42, 46, 48, 56, 63, 69, 72, 84, 92, 112, 126, 138, 144, 161, 168, 184, 207, 252, 276, 277, 322, 336, 368, 414, 483, 504, 552, 554, 644, 828, 831, 966, 1008, 1104, 1108, 1288, 1449, 1656, 1662, 1932, 1939, 2216, 2493, 2576, 2898, 3312, 3324, 3864, 3878, 4432, 4986, 5796, 5817, 6371, 6648, 7728, 7756, 9972, 11592, 11634, 12742, 13296, 15512, 17451, 19113, 19944, 23184, 23268, 25484, 31024, 34902, 38226, 39888, 44597, 46536, 50968, 57339, 69804, 76452, 89194, 93072, 101936, 114678, 133791, 139608, 152904, 178388, 229356, 267582, 279216, 305808, 356776, 401373, 458712, 535164, 713552, 802746, 917424, 1070328, 1605492, 2140656, 3210984, 6421968.
If you add them up, you will get the total of 21,510,528.