21805312 has 36 divisors (see below), whose sum is σ = 45826480. Its totient is φ = 10326528.

The previous prime is 21805297. The next prime is 21805327. The reversal of 21805312 is 21350812.

It is an interprime number because it is at equal distance from previous prime (21805297) and next prime (21805327).

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2623 + ... + 7105.

Almost surely, 2^21805312 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 21805312, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22913240).

21805312 is an abundant number, since it is smaller than the sum of its proper divisors (24021168).

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

21805312 is an equidigital number, since it uses as much as digits as its factorization.

21805312 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4518 (or 4504 counting only the distinct ones).

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

The square root of 21805312 is about 4669.6158300229. The cubic root of 21805312 is about 279.3749321769.

The spelling of 21805312 in words is "twenty-one million, eight hundred five thousand, three hundred twelve".