A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 890460 can be evenly divided by 1 2 3 4 5 6 9 10 12 15 17 18 20 27 30 34 36 45 51 54 60 68 85 90 97 102 108 135 153 170 180 194 204 255 270 291 306 340 388 459 485 510 540 582 612 765 873 918 970 1,020 1,164 1,455 1,530 1,649 1,746 1,836 1,940 2,295 2,619 2,910 3,060 3,298 3,492 4,365 4,590 4,947 5,238 5,820 6,596 8,245 8,730 9,180 9,894 10,476 13,095 14,841 16,490 17,460 19,788 24,735 26,190 29,682 32,980 44,523 49,470 52,380 59,364 74,205 89,046 98,940 148,410 178,092 222,615 296,820 445,230 and 890,460, with no remainder.
Since 890,460 cannot be divided by just 1 and 890,460, it is not a prime number.