A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2766624 can be evenly divided by 1 2 3 4 6 7 8 12 14 16 21 23 24 28 32 42 46 48 56 69 84 92 96 112 138 161 168 179 184 224 276 322 336 358 368 483 537 552 644 672 716 736 966 1,074 1,104 1,253 1,288 1,432 1,932 2,148 2,208 2,506 2,576 2,864 3,759 3,864 4,117 4,296 5,012 5,152 5,728 7,518 7,728 8,234 8,592 10,024 12,351 15,036 15,456 16,468 17,184 20,048 24,702 28,819 30,072 32,936 40,096 49,404 57,638 60,144 65,872 86,457 98,808 115,276 120,288 131,744 172,914 197,616 230,552 345,828 395,232 461,104 691,656 922,208 1,383,312 and 2,766,624, with no remainder.
Since 2,766,624 cannot be divided by just 1 and 2,766,624, it is not a prime number.