21331212 has 96 divisors (see below), whose sum is σ = 60662784. Its totient is φ = 5702400.

The previous prime is 21331201. The next prime is 21331217. The reversal of 21331212 is 21213312.

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

It is a junction number, because it is equal to n+sod(n) for n = 21331191 and 21331200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21331217) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 117762 + ... + 117942.

It is an arithmetic number, because the mean of its divisors is an integer number (631904).

Almost surely, 2^21331212 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21331212, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30331392).

21331212 is an abundant number, since it is smaller than the sum of its proper divisors (39331572).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21331212 is a wasteful number, since it uses less digits than its factorization.

21331212 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 279 (or 277 counting only the distinct ones).

The product of its digits is 72, while the sum is 15.

The square root of 21331212 is about 4618.5725067384. The cubic root of 21331212 is about 277.3353166206.

Adding to 21331212 its reverse (21213312), we get a palindrome (42544524).

The spelling of 21331212 in words is "twenty-one million, three hundred thirty-one thousand, two hundred twelve".