A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 578592 can be evenly divided by 1 2 3 4 6 7 8 9 12 14 16 18 21 24 28 32 36 41 42 48 49 56 63 72 82 84 96 98 112 123 126 144 147 164 168 196 224 246 252 287 288 294 328 336 369 392 441 492 504 574 588 656 672 738 784 861 882 984 1,008 1,148 1,176 1,312 1,476 1,568 1,722 1,764 1,968 2,009 2,016 2,296 2,352 2,583 2,952 3,444 3,528 3,936 4,018 4,592 4,704 5,166 5,904 6,027 6,888 7,056 8,036 9,184 10,332 11,808 12,054 13,776 14,112 16,072 18,081 20,664 24,108 27,552 32,144 36,162 41,328 48,216 64,288 72,324 82,656 96,432 144,648 192,864 289,296 and 578,592, with no remainder.
Since 578,592 cannot be divided by just 1 and 578,592, it is not a prime number.