21213321 has 16 divisors (see below), whose sum is σ = 29213184. Its totient is φ = 13682304.

The previous prime is 21213293. The next prime is 21213341. The reversal of 21213321 is 12331212.

It is not a de Polignac number, because 21213321 - 2⁷ = 21213193 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21213321.

It is not an unprimeable number, because it can be changed into a prime (21213341) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 24325 + ... + 25181.

It is an arithmetic number, because the mean of its divisors is an integer number (1825824).

Almost surely, 2^21213321 is an apocalyptic number.

It is an amenable number.

21213321 is a deficient number, since it is larger than the sum of its proper divisors (7999863).

21213321 is a wasteful number, since it uses less digits than its factorization.

21213321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1120.

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

The square root of 21213321 is about 4605.7921142839. The cubic root of 21213321 is about 276.8234570387.

Adding to 21213321 its reverse (12331212), we get a palindrome (33544533).

The spelling of 21213321 in words is "twenty-one million, two hundred thirteen thousand, three hundred twenty-one".