A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1630512 can be evenly divided by 1 2 3 4 6 8 9 12 13 16 18 24 26 36 39 48 52 67 72 78 104 117 134 144 156 169 201 208 234 268 312 338 402 468 507 536 603 624 676 804 871 936 1,014 1,072 1,206 1,352 1,521 1,608 1,742 1,872 2,028 2,412 2,613 2,704 3,042 3,216 3,484 4,056 4,824 5,226 6,084 6,968 7,839 8,112 9,648 10,452 11,323 12,168 13,936 15,678 20,904 22,646 24,336 31,356 33,969 41,808 45,292 62,712 67,938 90,584 101,907 125,424 135,876 181,168 203,814 271,752 407,628 543,504 815,256 and 1,630,512, with no remainder.
Since 1,630,512 cannot be divided by just 1 and 1,630,512, it is not a prime number.