A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2020536 can be evenly divided by 1 2 3 4 6 7 8 9 12 14 18 19 21 24 28 36 38 42 56 57 63 72 76 84 114 126 133 152 168 171 211 228 252 266 342 399 422 456 504 532 633 684 798 844 1,064 1,197 1,266 1,368 1,477 1,596 1,688 1,899 2,394 2,532 2,954 3,192 3,798 4,009 4,431 4,788 5,064 5,908 7,596 8,018 8,862 9,576 11,816 12,027 13,293 15,192 16,036 17,724 24,054 26,586 28,063 32,072 35,448 36,081 48,108 53,172 56,126 72,162 84,189 96,216 106,344 112,252 144,324 168,378 224,504 252,567 288,648 336,756 505,134 673,512 1,010,268 and 2,020,536, with no remainder.
Since 2,020,536 cannot be divided by just 1 and 2,020,536, it is not a prime number.