A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 831168 can be evenly divided by 1 2 3 4 6 8 9 12 13 16 18 24 26 27 32 36 37 39 48 52 54 64 72 74 78 96 104 108 111 117 144 148 156 192 208 216 222 234 288 296 312 333 351 416 432 444 468 481 576 592 624 666 702 832 864 888 936 962 999 1,184 1,248 1,332 1,404 1,443 1,728 1,776 1,872 1,924 1,998 2,368 2,496 2,664 2,808 2,886 3,552 3,744 3,848 3,996 4,329 5,328 5,616 5,772 7,104 7,488 7,696 7,992 8,658 10,656 11,232 11,544 12,987 15,392 15,984 17,316 21,312 22,464 23,088 25,974 30,784 31,968 34,632 46,176 51,948 63,936 69,264 92,352 103,896 138,528 207,792 277,056 415,584 and 831,168, with no remainder.
Since 831,168 cannot be divided by just 1 and 831,168, it is not a prime number.