A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 7538440 can be evenly divided by 1 2 4 5 7 8 10 13 14 19 20 26 28 35 38 40 52 56 65 70 76 91 95 104 109 130 133 140 152 182 190 218 247 260 266 280 364 380 436 455 494 520 532 545 665 728 760 763 872 910 988 1,064 1,090 1,235 1,330 1,417 1,526 1,729 1,820 1,976 2,071 2,180 2,470 2,660 2,834 3,052 3,458 3,640 3,815 4,142 4,360 4,940 5,320 5,668 6,104 6,916 7,085 7,630 8,284 8,645 9,880 9,919 10,355 11,336 13,832 14,170 14,497 15,260 16,568 17,290 19,838 20,710 26,923 28,340 28,994 30,520 34,580 39,676 41,420 49,595 53,846 56,680 57,988 69,160 72,485 79,352 82,840 99,190 107,692 115,976 134,615 144,970 188,461 198,380 215,384 269,230 289,940 376,922 396,760 538,460 579,880 753,844 942,305 1,076,920 1,507,688 1,884,610 3,769,220 and 7,538,440, with no remainder.
Since 7,538,440 cannot be divided by just 1 and 7,538,440, it is not a prime number.