2111

This number is a prime.

+ The square root of 4456321. (The reversal of 4456321 is 1112 squared.)

+ The smallest "prime year" of the 22nd century. The next prime years are 2113, 2129, 2131, 2137, 2141, 2143, 2153, 2161, and 2179.

+ 2111 in base b is prime for all values of b from 3 to 10, with the exception of b=6. [Necula]

+ The first salmonella outbreak associated with peanut butter had product code 2111 on the lid.

+ 2111 = 1 + 2^2 + 2^3 + 2^5 + 2^7 + 2^11. The exponents are consecutive primes. [Noe]

+ The smallest prime that together with its "look-and-say" description from the left in the digit-frequency order (i.e., 2 once, 1 thrice) forms a twin prime pair (2111, 2113) [Beedassy]

+ The smaller of only two primes less than a googol formed by concatenating in descending order the first n multidigit numbers ending with 1, (case n=2). The other is 41312111 for n=4. [Loungrides]

+ 2111 is the smallest start of a run of five primes obtained by the following procedure: replace each digit of 2111 with the digit's square to obtain a new prime, and up to five primes doing this recursively, i.e., 2111, 4111, 16111, 136111 and 1936111. [Rivera]

+ 2111 is the smallest four-digit prime which remains prime when 2 is added to any of its digits. [Petrov]

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

Printed from the PrimePages <primes.utm.edu> © G. L. Honaker and Chris K. Caldwell