A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 869440 can be evenly divided by 1 2 4 5 8 10 11 13 16 19 20 22 26 32 38 40 44 52 55 64 65 76 80 88 95 104 110 130 143 152 160 176 190 208 209 220 247 260 286 304 320 352 380 416 418 440 494 520 572 608 704 715 760 832 836 880 988 1,040 1,045 1,144 1,216 1,235 1,430 1,520 1,672 1,760 1,976 2,080 2,090 2,288 2,470 2,717 2,860 3,040 3,344 3,520 3,952 4,160 4,180 4,576 4,940 5,434 5,720 6,080 6,688 7,904 8,360 9,152 9,880 10,868 11,440 13,376 13,585 15,808 16,720 19,760 21,736 22,880 27,170 33,440 39,520 43,472 45,760 54,340 66,880 79,040 86,944 108,680 173,888 217,360 434,720 and 869,440, with no remainder.
Since 869,440 cannot be divided by just 1 and 869,440, it is not a prime number.