This number is a prime.

+ The smallest prime number that can be formed by concatenating the first four positive integers. [Murthy]

+ Joy of Thinking: The Beauty and Power of Classical Mathematical Ideas is The Teaching Company's course number 1423.

+ The smallest prime which is sum of composite numbers written with primes repeated twice for each term : 1423 = 22+33+55+1313 = 33+77+1313. [Capelle]

+ A 4-digit prime, which if repeated 4 times after number 4, yields another prime whose sum of digits is 44. [Silva]

+ The smallest 4-digit prime whose sum of the two leftmost digits (1 and 4) equals the sum of the two rightmost digits (2 and 3). [Forouhari]

(There are 2 curios for this number that have not yet been approved by an editor.)

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