This number is a prime.

+ 16561 = 9^2^2 + 10^2^2. [Imgregor]

+ The smallest palindromic prime consisting of the digits in which biquadrates of positive digits end. It is also the sum of biquadrates of two successive numbers, i.e., 9^4+10^4. [Loungrides]

+ The smallest multidigit palindromic Quartan prime. [Gupta]

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