A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1030320 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 16 18 20 24 27 30 36 40 45 48 53 54 60 72 80 81 90 106 108 120 135 144 159 162 180 212 216 240 243 265 270 318 324 360 405 424 432 477 486 530 540 636 648 720 795 810 848 954 972 1,060 1,080 1,215 1,272 1,296 1,431 1,590 1,620 1,908 1,944 2,120 2,160 2,385 2,430 2,544 2,862 3,180 3,240 3,816 3,888 4,240 4,293 4,770 4,860 5,724 6,360 6,480 7,155 7,632 8,586 9,540 9,720 11,448 12,720 12,879 14,310 17,172 19,080 19,440 21,465 22,896 25,758 28,620 34,344 38,160 42,930 51,516 57,240 64,395 68,688 85,860 103,032 114,480 128,790 171,720 206,064 257,580 343,440 515,160 and 1,030,320, with no remainder.
Since 1,030,320 cannot be divided by just 1 and 1,030,320, it is not a prime number.