A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3493920 can be evenly divided by 1 2 3 4 5 6 8 10 12 15 16 20 24 29 30 32 40 48 58 60 80 87 96 116 120 145 160 174 232 240 251 290 348 435 464 480 502 580 696 753 870 928 1,004 1,160 1,255 1,392 1,506 1,740 2,008 2,320 2,510 2,784 3,012 3,480 3,765 4,016 4,640 5,020 6,024 6,960 7,279 7,530 8,032 10,040 12,048 13,920 14,558 15,060 20,080 21,837 24,096 29,116 30,120 36,395 40,160 43,674 58,232 60,240 72,790 87,348 109,185 116,464 120,480 145,580 174,696 218,370 232,928 291,160 349,392 436,740 582,320 698,784 873,480 1,164,640 1,746,960 and 3,493,920, with no remainder.
Since 3,493,920 cannot be divided by just 1 and 3,493,920, it is not a prime number.