A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2890888 can be evenly divided by 1 2 4 7 8 11 13 14 19 22 26 28 38 44 52 56 76 77 88 91 104 133 143 152 154 182 209 247 266 286 308 361 364 418 494 532 572 616 722 728 836 988 1,001 1,064 1,144 1,444 1,463 1,672 1,729 1,976 2,002 2,527 2,717 2,888 2,926 3,458 3,971 4,004 4,693 5,054 5,434 5,852 6,916 7,942 8,008 9,386 10,108 10,868 11,704 13,832 15,884 18,772 19,019 20,216 21,736 27,797 31,768 32,851 37,544 38,038 51,623 55,594 65,702 76,076 103,246 111,188 131,404 152,152 206,492 222,376 262,808 361,361 412,984 722,722 1,445,444 and 2,890,888, with no remainder.
Since 2,890,888 cannot be divided by just 1 and 2,890,888, it is not a prime number.