21538304 has 80 divisors (see below), whose sum is σ = 47139840. Its totient is φ = 9799680.

The previous prime is 21538301. The next prime is 21538339. The reversal of 21538304 is 40383512.

It is a plaindrome in base 9.

It is a zygodrome in base 9.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21538301) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 365027 + ... + 365085.

It is an arithmetic number, because the mean of its divisors is an integer number (589248).

Almost surely, 2^21538304 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 21538304, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23569920).

21538304 is an abundant number, since it is smaller than the sum of its proper divisors (25601536).

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

21538304 is an equidigital number, since it uses as much as digits as its factorization.

21538304 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 131 (or 115 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 26.

The square root of 21538304 is about 4640.9378362568. The cubic root of 21538304 is about 278.2299221017.

The spelling of 21538304 in words is "twenty-one million, five hundred thirty-eight thousand, three hundred four".