21530304 has 42 divisors (see below), whose sum is σ = 61714380. Its totient is φ = 7176576.

The previous prime is 21530303. The next prime is 21530321. The reversal of 21530304 is 40303512.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21530303) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 18114 + ... + 19265.

It is an arithmetic number, because the mean of its divisors is an integer number (1469390).

Almost surely, 2^21530304 is an apocalyptic number.

21530304 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21530304 is an abundant number, since it is smaller than the sum of its proper divisors (40184076).

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

21530304 is a wasteful number, since it uses less digits than its factorization.

21530304 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37397 (or 37384 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 18.

The square root of 21530304 is about 4640.0758614488. The cubic root of 21530304 is about 278.1954700697.

Adding to 21530304 its reverse (40303512), we get a palindrome (61833816).

The spelling of 21530304 in words is "twenty-one million, five hundred thirty thousand, three hundred four".