21123321 has 4 divisors (see below), whose sum is σ = 28164432. Its totient is φ = 14082212.

The previous prime is 21123313. The next prime is 21123331. The reversal of 21123321 is 12332112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21123321 - 2³ = 21123313 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21123321.

It is not an unprimeable number, because it can be changed into a prime (21123301) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3520551 + ... + 3520556.

It is an arithmetic number, because the mean of its divisors is an integer number (7041108).

Almost surely, 2^21123321 is an apocalyptic number.

It is an amenable number.

21123321 is a deficient number, since it is larger than the sum of its proper divisors (7041111).

21123321 is an equidigital number, since it uses as much as digits as its factorization.

21123321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7041110.

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

The square root of 21123321 is about 4596.0114229623. The cubic root of 21123321 is about 276.4314167716.

Adding to 21123321 its reverse (12332112), we get a palindrome (33455433).

It can be divided in two parts, 211 and 23321, that added together give a palindrome (23532).

The spelling of 21123321 in words is "twenty-one million, one hundred twenty-three thousand, three hundred twenty-one".