21540320 has 48 divisors (see below), whose sum is σ = 51746688. Its totient is φ = 8471040.

The previous prime is 21540317. The next prime is 21540341. The reversal of 21540320 is 2304512.

It is a congruent number.

It is an unprimeable number.

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, 8657 + ... + 10863.

It is an arithmetic number, because the mean of its divisors is an integer number (1078056).

Almost surely, 2^21540320 is an apocalyptic number.

21540320 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 21540320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25873344).

21540320 is an abundant number, since it is smaller than the sum of its proper divisors (30206368).

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

21540320 is a wasteful number, since it uses less digits than its factorization.

21540320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2283 (or 2275 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 21540320 is about 4641.1550286540. The cubic root of 21540320 is about 278.2386026679.

Adding to 21540320 its reverse (2304512), we get a palindrome (23844832).

The spelling of 21540320 in words is "twenty-one million, five hundred forty thousand, three hundred twenty".