This number is a prime.

+ The smallest irregular prime having an irregularity index of 3. [Noe]

+ 491 is a Sophie Germain prime. 491 is also a divisor of a Generalized Fermat Number, as 491 * (2^123281+1) divides GF(123280,10) = 10^(2^123280) + 1. [Carmichael]

+ 10000^491-491 is the smallest titanic prime of form 10000^n-n, where n is prime. [Loungrides]

+ The sum of first two Lychrel numbers is prime, i.e., 196+295. [Loungrides]

+ It is conjectured that 491 is the smallest prime not of the form x3 + y3 + 2z3. [Wesolowski]

+ 10000^491-491 is prime. 491 is the smallest number with this property. [Bajpai]

+ The smallest prime p such that 10*p + 3 is a perfect cube. [Ewing]

+ The smallest prime p such that the sum of digits of m^p is never equal to m except for m=1. [Gupta]

(There are 4 curios for this number that have not yet been approved by an editor.)

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