A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 964656 can be evenly divided by 1 2 3 4 6 7 8 9 11 12 14 16 18 21 22 24 27 28 29 33 36 42 44 48 54 56 58 63 66 72 77 84 87 88 99 108 112 116 126 132 144 154 168 174 176 189 198 203 216 231 232 252 261 264 297 308 319 336 348 378 396 406 432 462 464 504 522 528 594 609 616 638 693 696 756 783 792 812 924 957 1,008 1,044 1,188 1,218 1,232 1,276 1,386 1,392 1,512 1,566 1,584 1,624 1,827 1,848 1,914 2,079 2,088 2,233 2,376 2,436 2,552 2,772 2,871 3,024 3,132 3,248 3,654 3,696 3,828 4,158 4,176 4,466 4,752 4,872 5,104 5,481 5,544 5,742 6,264 6,699 7,308 7,656 8,316 8,613 8,932 9,744 10,962 11,088 11,484 12,528 13,398 14,616 15,312 16,632 17,226 17,864 20,097 21,924 22,968 26,796 29,232 33,264 34,452 35,728 40,194 43,848 45,936 53,592 60,291 68,904 80,388 87,696 107,184 120,582 137,808 160,776 241,164 321,552 482,328 and 964,656, with no remainder.
Since 964,656 cannot be divided by just 1 and 964,656, it is not a prime number.