A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 7991676 can be evenly divided by 1 2 3 4 6 7 9 11 12 14 18 21 22 27 28 31 33 36 42 44 54 62 63 66 77 84 93 99 108 124 126 132 154 186 189 198 217 231 252 279 297 308 341 372 378 396 434 462 558 594 651 682 693 756 837 868 924 961 1,023 1,116 1,188 1,302 1,364 1,386 1,674 1,922 1,953 2,046 2,079 2,387 2,604 2,772 2,883 3,069 3,348 3,844 3,906 4,092 4,158 4,774 5,766 5,859 6,138 6,727 7,161 7,812 8,316 8,649 9,207 9,548 10,571 11,532 11,718 12,276 13,454 14,322 17,298 18,414 20,181 21,142 21,483 23,436 25,947 26,908 28,644 31,713 34,596 36,828 40,362 42,284 42,966 51,894 60,543 63,426 64,449 73,997 80,724 85,932 95,139 103,788 121,086 126,852 128,898 147,994 181,629 190,278 221,991 242,172 257,796 285,417 295,988 363,258 380,556 443,982 570,834 665,973 726,516 887,964 1,141,668 1,331,946 1,997,919 2,663,892 3,995,838 and 7,991,676, with no remainder.
Since 7,991,676 cannot be divided by just 1 and 7,991,676, it is not a prime number.