A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 945516 can be evenly divided by 1 2 3 4 6 11 12 13 19 22 26 29 33 38 39 44 52 57 58 66 76 78 87 114 116 132 143 156 174 209 228 247 286 319 348 377 418 429 494 551 572 627 638 741 754 836 858 957 988 1,102 1,131 1,254 1,276 1,482 1,508 1,653 1,716 1,914 2,204 2,262 2,508 2,717 2,964 3,306 3,828 4,147 4,524 5,434 6,061 6,612 7,163 8,151 8,294 10,868 12,122 12,441 14,326 16,302 16,588 18,183 21,489 24,244 24,882 28,652 32,604 36,366 42,978 49,764 72,732 78,793 85,956 157,586 236,379 315,172 472,758 and 945,516, with no remainder.
Since 945,516 cannot be divided by just 1 and 945,516, it is not a prime number.