A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2652624 can be evenly divided by 1 2 3 4 6 8 9 12 13 16 18 24 26 36 39 48 52 72 78 104 109 117 144 156 169 208 218 234 312 327 338 436 468 507 624 654 676 872 936 981 1,014 1,308 1,352 1,417 1,521 1,744 1,872 1,962 2,028 2,616 2,704 2,834 3,042 3,924 4,056 4,251 5,232 5,668 6,084 7,848 8,112 8,502 11,336 12,168 12,753 15,696 17,004 18,421 22,672 24,336 25,506 34,008 36,842 51,012 55,263 68,016 73,684 102,024 110,526 147,368 165,789 204,048 221,052 294,736 331,578 442,104 663,156 884,208 1,326,312 and 2,652,624, with no remainder.
Since 2,652,624 cannot be divided by just 1 and 2,652,624, it is not a prime number.