21212 has 6 divisors (see below), whose sum is σ = 37128. Its totient is φ = 10604.

The previous prime is 21211. The next prime is 21221.

21212 is nontrivially palindromic in base 10.

21212 is an esthetic number in base 10, because in such base its adjacent digits differ by 1.

It is a nude number because it is divisible by every one of its digits.

It is an alternating number because its digits alternate between even and odd.

21212 is an undulating number in base 10.

It is a nialpdrome in base 15.

It is a self number, because there is not a number n which added to its sum of digits gives 21212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2648 + ... + 2655.

It is an arithmetic number, because the mean of its divisors is an integer number (6188).

2²¹²¹² is an apocalyptic number.

It is an amenable number.

21212 is a deficient number, since it is larger than the sum of its proper divisors (15916).

21212 is a wasteful number, since it uses less digits than its factorization.

21212 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5307 (or 5305 counting only the distinct ones).

The product of its digits is 8, while the sum is 8.

The square root of 21212 is about 145.6434001251. The cubic root of 21212 is about 27.6817710785.

The spelling of 21212 in words is "twenty-one thousand, two hundred twelve", and thus it is an iban number.