Why even number of digit prime palindromes are not possible?
\nBecause even length prime digit numbers are divisible by 11 therefore are not prime.\nIt\'s a trick that has to do powers of 10 and mod 11.\nEx: 10 = 10^1 mod
```\nBecause even length prime digit numbers are divisible by 11 therefore are not prime.\nIt\'s a trick that has to do powers of 10 and mod 11.\nEx: 10 = 10^1 mod 11 = -1 mod 11\n      100 = 10^2 = 1 mod 11\n      1000 = 10^3 = -1 mod 11\n      10000 = 10^4 = 1 mod 11\nSee the pattern? \nEven exponent powers of 10 are 1 mod 11 \nOdd exponent powers of 10 are -1 mod 11.\n\nWe also know decimal numbers are just base 10 expansion of the digits.\n\nSo   1225 = (10^3*)1 + 2*(10^2) + 2*(10^1) + 5*(10^0).\n        using modular arithmetic we can say,\n \n        1225 MOD 11 = (-1)*1 + 2*(1) + 2*(-1) + 5*(1) = -1 + 2 - 2 + 5 = 4.\n\n        In other words, in MOD 11 we calculate what a decimal number is by just alternating the addition and subtraction across the digits.\n\nAnother example.\n\n    1323412 MOD 11 =   1 -3  +2 -3 +4 -1 +2 MOD 11 = 0. (x MOD 11 == 0) => 11 \'divides\' x\nThen it becomes quite obvious why the above logic works for even palindromes.\n\nExample: \n\n321123 =      -3 + 2 - 1 + 1 -2 + 3 = 0. All the numbers cancel out with each other.\n\n```
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