A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6171648 can be evenly divided by 1 2 3 4 6 7 8 12 14 16 21 24 28 32 41 42 48 49 56 64 82 84 96 98 112 123 128 147 164 168 192 196 224 246 256 287 294 328 336 384 392 448 492 512 574 588 656 672 768 784 861 896 984 1,024 1,148 1,176 1,312 1,344 1,536 1,568 1,722 1,792 1,968 2,009 2,296 2,352 2,624 2,688 3,072 3,136 3,444 3,584 3,936 4,018 4,592 4,704 5,248 5,376 6,027 6,272 6,888 7,168 7,872 8,036 9,184 9,408 10,496 10,752 12,054 12,544 13,776 15,744 16,072 18,368 18,816 20,992 21,504 24,108 25,088 27,552 31,488 32,144 36,736 37,632 41,984 48,216 50,176 55,104 62,976 64,288 73,472 75,264 96,432 110,208 125,952 128,576 146,944 150,528 192,864 220,416 257,152 293,888 385,728 440,832 514,304 771,456 881,664 1,028,608 1,542,912 2,057,216 3,085,824 and 6,171,648, with no remainder.
Since 6,171,648 cannot be divided by just 1 and 6,171,648, it is not a prime number.