21805321 has 8 divisors (see below), whose sum is σ = 22872960. Its totient is φ = 20762928.

The previous prime is 21805297. The next prime is 21805327. The reversal of 21805321 is 12350812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21805321 - 2¹³ = 21797129 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21805292 and 21805301.

It is not an unprimeable number, because it can be changed into a prime (21805327) 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 7 ways as a sum of consecutive naturals, for example, 4531 + ... + 8008.

It is an arithmetic number, because the mean of its divisors is an integer number (2859120).

Almost surely, 2^21805321 is an apocalyptic number.

It is an amenable number.

21805321 is a deficient number, since it is larger than the sum of its proper divisors (1067639).

21805321 is a wasteful number, since it uses less digits than its factorization.

21805321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12623.

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 21805321 is about 4669.6167936995. The cubic root of 21805321 is about 279.3749706136.

The spelling of 21805321 in words is "twenty-one million, eight hundred five thousand, three hundred twenty-one".