It is a happy number.
2121 is an esthetic number in base 10, because in such base its adjacent digits differ by 1.
It is a sphenic number, since it is the product of 3 distinct primes.
It is an alternating number because its digits alternate between even and odd.
2121 is an undulating number in base 10.
It is a Curzon number.
2121 is a lucky number.
It is a plaindrome in base 12.
It is a nialpdrome in base 8, base 13 and base 15.
2121 is a gapful number since it is divisible by the number (21) formed by its first and last digit.
It is an amenable number.
2121 is a wasteful number, since it uses less digits than its factorization.
2121 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 111.
The square root of 2121 is about 46.0543157587. The cubic root of 2121 is about 12.8483361207.
Adding to 2121 its reverse (1212), we get a palindrome (3333).
Subtracting from 2121 its reverse (1212), we obtain a palindrome (909).
The spelling of 2121 in words is "two thousand, one hundred twenty-one", and thus it is an iban number.