A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1637064 can be evenly divided by 1 2 3 4 6 8 9 11 12 13 18 22 24 26 27 33 36 39 44 52 53 54 66 72 78 88 99 104 106 108 117 132 143 156 159 198 212 216 234 264 286 297 312 318 351 396 424 429 468 477 572 583 594 636 689 702 792 858 936 954 1,144 1,166 1,188 1,272 1,287 1,378 1,404 1,431 1,716 1,749 1,908 2,067 2,332 2,376 2,574 2,756 2,808 2,862 3,432 3,498 3,816 3,861 4,134 4,664 5,148 5,247 5,512 5,724 6,201 6,996 7,579 7,722 8,268 10,296 10,494 11,448 12,402 13,992 15,158 15,444 15,741 16,536 18,603 20,988 22,737 24,804 30,316 30,888 31,482 37,206 41,976 45,474 49,608 60,632 62,964 68,211 74,412 90,948 125,928 136,422 148,824 181,896 204,633 272,844 409,266 545,688 818,532 and 1,637,064, with no remainder.
Since 1,637,064 cannot be divided by just 1 and 1,637,064, it is not a prime number.