This number is a composite.

+ Every number greater than 121 is the sum of distinct primes of the form 4n + 1. [Wells]

+ The smallest palindromic composite such that some permutation of digits is prime.

+ 121 is the only odd palindromic square with an odd number of digits that is divisible by a palindromic prime number with an even number of digits. [Luhn]

+ Smallest palindrome pseudoprime to base 3. [De Geest]

+ A palindrome whose prime factors are palindromic. [Russo]

+ 121 can be expressed as the sum of a prime and its reversal for exactly three distinct primes. [Patterson]

+ The smallest three-digit number such that the sum of the values that result by placing the exponentation symbol (^) between any two consecutive digits is prime (i.e., 1^21+12^1 is prime.) [Opao]

+ 121, 143, 169, and 187 are the first and possibly only four consecutive brilliant numbers whose reverses are also brilliant numbers. [Gaydos]

+ Let's check if 121 is a Prime number. [Daredia]

(There are 5 curios for this number that have not yet been approved by an editor.)

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