26

Number
$26$ (twenty-six) is:


 * $2 \times 13$


 * The smallest non-palindromic integer whose square is palindromic:
 * $26^2 = 676$


 * The $2$nd noncototient:
 * $\nexists m \in \Z_{>0}: m - \phi \left({m}\right) = 26$
 * where $\phi \left({m}\right)$ denotes the Euler $\phi$ function


 * Equal to the sum of the digits of its cube:
 * $26^3 = 17 \, 576$; $1 + 7 + 5 + 7 + 6 = 26$


 * Cannot be represented by the sum of less than $6$ hexagonal numbers:
 * $26 = 6 + 6 + 6 + 6 + 1 + 1$

Also see

 * Smallest Non-Palindromic Number with Palindromic Square
 * Positive Integers Equal to Sum of Digits of Cube