21230720 has 96 divisors (see below), whose sum is σ = 59128380. Its totient is φ = 7268352.

The previous prime is 21230719. The next prime is 21230749. The reversal of 21230720 is 2703212.

It can be written as a sum of positive squares in 2 ways, for example, as 19571776 + 1658944 = 4424^2 + 1288^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 31022 + ... + 31698.

Almost surely, 2^21230720 is an apocalyptic number.

21230720 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 21230720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29564190).

21230720 is an abundant number, since it is smaller than the sum of its proper divisors (37897660).

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

21230720 is an equidigital number, since it uses as much as digits as its factorization.

21230720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 710 (or 691 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 17.

The square root of 21230720 is about 4607.6805444822. The cubic root of 21230720 is about 276.8991191683.

Adding to 21230720 its reverse (2703212), we get a palindrome (23933932).

The spelling of 21230720 in words is "twenty-one million, two hundred thirty thousand, seven hundred twenty".