A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3261024 can be evenly divided by 1 2 3 4 6 8 9 12 13 16 18 24 26 32 36 39 48 52 67 72 78 96 104 117 134 144 156 169 201 208 234 268 288 312 338 402 416 468 507 536 603 624 676 804 871 936 1,014 1,072 1,206 1,248 1,352 1,521 1,608 1,742 1,872 2,028 2,144 2,412 2,613 2,704 3,042 3,216 3,484 3,744 4,056 4,824 5,226 5,408 6,084 6,432 6,968 7,839 8,112 9,648 10,452 11,323 12,168 13,936 15,678 16,224 19,296 20,904 22,646 24,336 27,872 31,356 33,969 41,808 45,292 48,672 62,712 67,938 83,616 90,584 101,907 125,424 135,876 181,168 203,814 250,848 271,752 362,336 407,628 543,504 815,256 1,087,008 1,630,512 and 3,261,024, with no remainder.
Since 3,261,024 cannot be divided by just 1 and 3,261,024, it is not a prime number.