A truncatable prime is a leading digit is successively removed, then all resulting numbers are prime.
When given a number, Return as per the precedence given
1) 0 - if a number is not a prime or not a truncatable prime.
2) 5 - if a number is left-and-right-truncatable prime. E.g. - 127 => 2
3) 9 - if a number is left as well as right truncatable prime but not a left-and-right-truncatable prime.
For e.g - 313 => 13 (left) & 31 (right) but not 1 (left-and-right both)
4) 3 - if a number is (exclusive) left-truncatable prime. E.g - 17 => 7
7 - if a number is (exclusive) right-truncatable prime. E.g. - 29 => 2
Note - String functions are not allowed!
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William David Hill Dyuman Joshi Christian Schröder

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