A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1397400 can be evenly divided by 1 2 3 4 5 6 8 10 12 15 17 20 24 25 30 34 40 50 51 60 68 75 85 100 102 120 136 137 150 170 200 204 255 274 300 340 408 411 425 510 548 600 680 685 822 850 1,020 1,096 1,275 1,370 1,644 1,700 2,040 2,055 2,329 2,550 2,740 3,288 3,400 3,425 4,110 4,658 5,100 5,480 6,850 6,987 8,220 9,316 10,200 10,275 11,645 13,700 13,974 16,440 18,632 20,550 23,290 27,400 27,948 34,935 41,100 46,580 55,896 58,225 69,870 82,200 93,160 116,450 139,740 174,675 232,900 279,480 349,350 465,800 698,700 and 1,397,400, with no remainder.
Since 1,397,400 cannot be divided by just 1 and 1,397,400, it is not a prime number.