It just so happens that if a statement is true then its index number appears among the number's digits, and if a statement is false then its index number does not appear among the number's digits.

- The sum of the number's digits is a prime.
- The product of the number's digits is odd.
- Each of the number's digits is less than the next digit (if there is one).
- No two of the number's digits are equal.
- None of the number's digits is greater than 4.
- The number has fewer than 6 digits.
- The product of the number's digits is not divisible by 6.
- The number is even.
- No two of the number's digits differ by 1.
- At least one of the number's digits is equal to the sum of two other digits. (Any of the digits may be equal, as long as all 3 digits are distinct... for example: {2, 2, 4} or {2, 3, 5} )