12211221

Appears in sequences

• Numbers n such that the set S(n) = {k: k + reverse(k) = n} is not empty, at least one element of S(n) has the same number of digits as n and at least one element of S(n) has one digit less than n has.at n=19A088171
• Dates after Jan 01 1000 which are palindromic when they are written according to the ISO-8601-format YYYYMMDD.at n=28A210884
• Dates after Jan 01 1000 in chronological order which are palindromic when they are written according to the format MMDDYYYY (American standard). Leading zeros of the terms are suppressed.at n=28A210893
• List of imprimitive words over the alphabet {1,2}.at n=28A213972
• Squares in the Thue-Morse word A001285.at n=6A225186
• Smallest number with a n-character traditional Japanese notation.at n=14A384792