A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2228688 can be evenly divided by 1 2 3 4 6 7 8 9 11 12 14 16 18 21 22 24 27 28 33 36 42 44 48 54 56 63 66 67 72 77 84 88 99 108 112 126 132 134 144 154 168 176 189 198 201 216 231 252 264 268 297 308 336 378 396 402 432 462 469 504 528 536 594 603 616 693 737 756 792 804 924 938 1,008 1,072 1,188 1,206 1,232 1,386 1,407 1,474 1,512 1,584 1,608 1,809 1,848 1,876 2,079 2,211 2,376 2,412 2,772 2,814 2,948 3,024 3,216 3,618 3,696 3,752 4,158 4,221 4,422 4,752 4,824 5,159 5,544 5,628 5,896 6,633 7,236 7,504 8,316 8,442 8,844 9,648 10,318 11,088 11,256 11,792 12,663 13,266 14,472 15,477 16,632 16,884 17,688 19,899 20,636 22,512 25,326 26,532 28,944 30,954 33,264 33,768 35,376 39,798 41,272 46,431 50,652 53,064 61,908 67,536 79,596 82,544 92,862 101,304 106,128 123,816 139,293 159,192 185,724 202,608 247,632 278,586 318,384 371,448 557,172 742,896 1,114,344 and 2,228,688, with no remainder.
Since 2,228,688 cannot be divided by just 1 and 2,228,688, it is not a prime number.