A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2258880 can be evenly divided by 1 2 3 4 5 6 8 10 12 13 15 16 20 24 26 30 32 39 40 48 52 60 64 65 78 80 96 104 120 130 156 160 181 192 195 208 240 260 312 320 362 390 416 480 520 543 624 724 780 832 905 960 1,040 1,086 1,248 1,448 1,560 1,810 2,080 2,172 2,353 2,496 2,715 2,896 3,120 3,620 4,160 4,344 4,706 5,430 5,792 6,240 7,059 7,240 8,688 9,412 10,860 11,584 11,765 12,480 14,118 14,480 17,376 18,824 21,720 23,530 28,236 28,960 34,752 35,295 37,648 43,440 47,060 56,472 57,920 70,590 75,296 86,880 94,120 112,944 141,180 150,592 173,760 188,240 225,888 282,360 376,480 451,776 564,720 752,960 1,129,440 and 2,258,880, with no remainder.
Since 2,258,880 cannot be divided by just 1 and 2,258,880, it is not a prime number.