A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1393740 can be evenly divided by 1 2 3 4 5 6 9 10 12 15 18 20 27 29 30 36 45 54 58 60 87 89 90 108 116 135 145 174 178 180 261 267 270 290 348 356 435 445 522 534 540 580 783 801 870 890 1,044 1,068 1,305 1,335 1,566 1,602 1,740 1,780 2,403 2,581 2,610 2,670 3,132 3,204 3,915 4,005 4,806 5,162 5,220 5,340 7,743 7,830 8,010 9,612 10,324 12,015 12,905 15,486 15,660 16,020 23,229 24,030 25,810 30,972 38,715 46,458 48,060 51,620 69,687 77,430 92,916 116,145 139,374 154,860 232,290 278,748 348,435 464,580 696,870 and 1,393,740, with no remainder.
Since 1,393,740 cannot be divided by just 1 and 1,393,740, it is not a prime number.