21320320 has 64 divisors (see below), whose sum is σ = 58262400. Its totient is φ = 7308288.

The previous prime is 21320317. The next prime is 21320323. The reversal of 21320320 is 2302312.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21320317) and next prime (21320323).

It is a tau number, because it is divible by the number of its divisors (64).

It is a self number, because there is not a number n which added to its sum of digits gives 21320320.

It is not an unprimeable number, because it can be changed into a prime (21320323) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2101 + ... + 6859.

It is an arithmetic number, because the mean of its divisors is an integer number (910350).

Almost surely, 2^21320320 is an apocalyptic number.

21320320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21320320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29131200).

21320320 is an abundant number, since it is smaller than the sum of its proper divisors (36942080).

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

21320320 is an equidigital number, since it uses as much as digits as its factorization.

21320320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4785 (or 4773 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 13.

The square root of 21320320 is about 4617.3932039626. The cubic root of 21320320 is about 277.2881048861.

Adding to 21320320 its reverse (2302312), we get a palindrome (23622632).

The spelling of 21320320 in words is "twenty-one million, three hundred twenty thousand, three hundred twenty".