21321213 has 16 divisors (see below), whose sum is σ = 30916800. Its totient is φ = 13015296.

The previous prime is 21321203. The next prime is 21321217. The reversal of 21321213 is 31212312.

It is not a de Polignac number, because 21321213 - 2⁴ = 21321197 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21321192 and 21321201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21321217) 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, 3763 + ... + 7536.

It is an arithmetic number, because the mean of its divisors is an integer number (1932300).

Almost surely, 2^21321213 is an apocalyptic number.

It is an amenable number.

21321213 is a deficient number, since it is larger than the sum of its proper divisors (9595587).

21321213 is a wasteful number, since it uses less digits than its factorization.

21321213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11356.

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

The square root of 21321213 is about 4617.4899025336. The cubic root of 21321213 is about 277.2919762292.

Adding to 21321213 its reverse (31212312), we get a palindrome (52533525).

The spelling of 21321213 in words is "twenty-one million, three hundred twenty-one thousand, two hundred thirteen".