A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 606144 can be evenly divided by 1 2 3 4 6 7 8 11 12 14 16 21 22 24 28 32 33 41 42 44 48 56 64 66 77 82 84 88 96 112 123 132 154 164 168 176 192 224 231 246 264 287 308 328 336 352 448 451 462 492 528 574 616 656 672 704 861 902 924 984 1,056 1,148 1,232 1,312 1,344 1,353 1,722 1,804 1,848 1,968 2,112 2,296 2,464 2,624 2,706 3,157 3,444 3,608 3,696 3,936 4,592 4,928 5,412 6,314 6,888 7,216 7,392 7,872 9,184 9,471 10,824 12,628 13,776 14,432 14,784 18,368 18,942 21,648 25,256 27,552 28,864 37,884 43,296 50,512 55,104 75,768 86,592 101,024 151,536 202,048 303,072 and 606,144, with no remainder.
Since 606,144 cannot be divided by just 1 and 606,144, it is not a prime number.