A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3768688 can be evenly divided by 1 2 4 7 8 11 14 16 19 22 23 28 38 44 46 49 56 76 77 88 92 98 112 133 152 154 161 176 184 196 209 253 266 304 308 322 368 392 418 437 506 532 539 616 644 784 836 874 931 1,012 1,064 1,078 1,127 1,232 1,288 1,463 1,672 1,748 1,771 1,862 2,024 2,128 2,156 2,254 2,576 2,926 3,059 3,344 3,496 3,542 3,724 4,048 4,312 4,508 4,807 5,852 6,118 6,992 7,084 7,448 8,624 9,016 9,614 10,241 11,704 12,236 12,397 14,168 14,896 18,032 19,228 20,482 21,413 23,408 24,472 24,794 28,336 33,649 38,456 40,964 42,826 48,944 49,588 67,298 76,912 81,928 85,652 99,176 134,596 163,856 171,304 198,352 235,543 269,192 342,608 471,086 538,384 942,172 1,884,344 and 3,768,688, with no remainder.
Since 3,768,688 cannot be divided by just 1 and 3,768,688, it is not a prime number.