A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6388032 can be evenly divided by 1 2 3 4 6 7 8 12 14 16 21 24 28 32 42 48 49 56 64 84 96 97 98 112 147 168 192 194 196 224 291 294 336 343 388 392 448 582 588 672 679 686 776 784 1,029 1,164 1,176 1,344 1,358 1,372 1,552 1,568 2,037 2,058 2,328 2,352 2,716 2,744 3,104 3,136 4,074 4,116 4,656 4,704 4,753 5,432 5,488 6,208 8,148 8,232 9,312 9,408 9,506 10,864 10,976 14,259 16,296 16,464 18,624 19,012 21,728 21,952 28,518 32,592 32,928 33,271 38,024 43,456 57,036 65,184 65,856 66,542 76,048 99,813 114,072 130,368 133,084 152,096 199,626 228,144 266,168 304,192 399,252 456,288 532,336 798,504 912,576 1,064,672 1,597,008 2,129,344 3,194,016 and 6,388,032, with no remainder.
Since 6,388,032 cannot be divided by just 1 and 6,388,032, it is not a prime number.