A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 7826688 can be evenly divided by 1 2 3 4 6 8 9 12 16 18 24 32 36 43 48 64 72 79 86 96 128 129 144 158 172 192 237 256 258 288 316 344 384 387 474 516 576 632 688 711 768 774 948 1,032 1,152 1,264 1,376 1,422 1,548 1,896 2,064 2,304 2,528 2,752 2,844 3,096 3,397 3,792 4,128 5,056 5,504 5,688 6,192 6,794 7,584 8,256 10,112 10,191 11,008 11,376 12,384 13,588 15,168 16,512 20,224 20,382 22,752 24,768 27,176 30,336 30,573 33,024 40,764 45,504 49,536 54,352 60,672 61,146 81,528 91,008 99,072 108,704 122,292 163,056 182,016 217,408 244,584 326,112 434,816 489,168 652,224 869,632 978,336 1,304,448 1,956,672 2,608,896 3,913,344 and 7,826,688, with no remainder.
Since 7,826,688 cannot be divided by just 1 and 7,826,688, it is not a prime number.