A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 5641776 can be evenly divided by 1 2 3 4 6 7 8 9 12 14 16 18 21 24 28 29 36 42 48 56 58 63 72 84 87 112 116 126 144 168 174 193 203 232 252 261 336 348 386 406 464 504 522 579 609 696 772 812 1,008 1,044 1,158 1,218 1,351 1,392 1,544 1,624 1,737 1,827 2,088 2,316 2,436 2,702 3,088 3,248 3,474 3,654 4,053 4,176 4,632 4,872 5,404 5,597 6,948 7,308 8,106 9,264 9,744 10,808 11,194 12,159 13,896 14,616 16,212 16,791 21,616 22,388 24,318 27,792 29,232 32,424 33,582 39,179 44,776 48,636 50,373 64,848 67,164 78,358 89,552 97,272 100,746 117,537 134,328 156,716 194,544 201,492 235,074 268,656 313,432 352,611 402,984 470,148 626,864 705,222 805,968 940,296 1,410,444 1,880,592 2,820,888 and 5,641,776, with no remainder.
Since 5,641,776 cannot be divided by just 1 and 5,641,776, it is not a prime number.