A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1088472 can be evenly divided by 1 2 3 4 6 7 8 11 12 14 19 21 22 24 28 31 33 38 42 44 56 57 62 66 76 77 84 88 93 114 124 132 133 152 154 168 186 209 217 228 231 248 264 266 308 341 372 399 418 434 456 462 532 589 616 627 651 682 744 798 836 868 924 1,023 1,064 1,178 1,254 1,302 1,364 1,463 1,596 1,672 1,736 1,767 1,848 2,046 2,356 2,387 2,508 2,604 2,728 2,926 3,192 3,534 4,092 4,123 4,389 4,712 4,774 5,016 5,208 5,852 6,479 7,068 7,161 8,184 8,246 8,778 9,548 11,704 12,369 12,958 14,136 14,322 16,492 17,556 19,096 19,437 24,738 25,916 28,644 32,984 35,112 38,874 45,353 49,476 51,832 57,288 77,748 90,706 98,952 136,059 155,496 181,412 272,118 362,824 544,236 and 1,088,472, with no remainder.
Since 1,088,472 cannot be divided by just 1 and 1,088,472, it is not a prime number.