A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1904400 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 16 18 20 23 24 25 30 36 40 45 46 48 50 60 69 72 75 80 90 92 100 115 120 138 144 150 180 184 200 207 225 230 240 276 300 345 360 368 400 414 450 460 529 552 575 600 690 720 828 900 920 1,035 1,058 1,104 1,150 1,200 1,380 1,587 1,656 1,725 1,800 1,840 2,070 2,116 2,300 2,645 2,760 3,174 3,312 3,450 3,600 4,140 4,232 4,600 4,761 5,175 5,290 5,520 6,348 6,900 7,935 8,280 8,464 9,200 9,522 10,350 10,580 12,696 13,225 13,800 15,870 16,560 19,044 20,700 21,160 23,805 25,392 26,450 27,600 31,740 38,088 39,675 41,400 42,320 47,610 52,900 63,480 76,176 79,350 82,800 95,220 105,800 119,025 126,960 158,700 190,440 211,600 238,050 317,400 380,880 476,100 634,800 952,200 and 1,904,400, with no remainder.
Since 1,904,400 cannot be divided by just 1 and 1,904,400, it is not a prime number.