A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1774656 can be evenly divided by 1 2 3 4 6 8 9 12 13 16 18 24 26 27 32 36 39 48 52 54 64 72 78 79 96 104 108 117 144 156 158 192 208 216 234 237 288 312 316 351 416 432 468 474 576 624 632 702 711 832 864 936 948 1,027 1,248 1,264 1,404 1,422 1,728 1,872 1,896 2,054 2,133 2,496 2,528 2,808 2,844 3,081 3,744 3,792 4,108 4,266 5,056 5,616 5,688 6,162 7,488 7,584 8,216 8,532 9,243 11,232 11,376 12,324 15,168 16,432 17,064 18,486 22,464 22,752 24,648 27,729 32,864 34,128 36,972 45,504 49,296 55,458 65,728 68,256 73,944 98,592 110,916 136,512 147,888 197,184 221,832 295,776 443,664 591,552 887,328 and 1,774,656, with no remainder.
Since 1,774,656 cannot be divided by just 1 and 1,774,656, it is not a prime number.