A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1409940 can be evenly divided by 1 2 3 4 5 6 7 9 10 12 14 15 18 20 21 27 28 30 35 36 42 45 54 60 63 70 84 90 105 108 126 135 140 180 189 210 252 270 315 373 378 420 540 630 746 756 945 1,119 1,260 1,492 1,865 1,890 2,238 2,611 3,357 3,730 3,780 4,476 5,222 5,595 6,714 7,460 7,833 10,071 10,444 11,190 13,055 13,428 15,666 16,785 20,142 22,380 23,499 26,110 31,332 33,570 39,165 40,284 46,998 50,355 52,220 67,140 70,497 78,330 93,996 100,710 117,495 140,994 156,660 201,420 234,990 281,988 352,485 469,980 704,970 and 1,409,940, with no remainder.
Since 1,409,940 cannot be divided by just 1 and 1,409,940, it is not a prime number.