A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6484400 can be evenly divided by 1 2 4 5 8 10 13 16 20 25 26 29 40 43 50 52 58 65 80 86 100 104 116 130 145 172 200 208 215 232 260 290 325 344 377 400 430 464 520 559 580 650 688 725 754 860 1,040 1,075 1,118 1,160 1,247 1,300 1,450 1,508 1,720 1,885 2,150 2,236 2,320 2,494 2,600 2,795 2,900 3,016 3,440 3,770 4,300 4,472 4,988 5,200 5,590 5,800 6,032 6,235 7,540 8,600 8,944 9,425 9,976 11,180 11,600 12,470 13,975 15,080 16,211 17,200 18,850 19,952 22,360 24,940 27,950 30,160 31,175 32,422 37,700 44,720 49,880 55,900 62,350 64,844 75,400 81,055 99,760 111,800 124,700 129,688 150,800 162,110 223,600 249,400 259,376 324,220 405,275 498,800 648,440 810,550 1,296,880 1,621,100 3,242,200 and 6,484,400, with no remainder.
Since 6,484,400 cannot be divided by just 1 and 6,484,400, it is not a prime number.