21530288 has 20 divisors (see below), whose sum is σ = 44924208. Its totient is φ = 9936960.

The previous prime is 21530281. The next prime is 21530291. The reversal of 21530288 is 88203512.

It is a self number, because there is not a number n which added to its sum of digits gives 21530288.

It is not an unprimeable number, because it can be changed into a prime (21530281) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 51548 + ... + 51963.

Almost surely, 2^21530288 is an apocalyptic number.

It is an amenable number.

21530288 is an abundant number, since it is smaller than the sum of its proper divisors (23393920).

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

21530288 is a wasteful number, since it uses less digits than its factorization.

21530288 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 103532 (or 103526 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 29.

The square root of 21530288 is about 4640.0741373388. The cubic root of 21530288 is about 278.1954011571.

It can be divided in two parts, 215 and 30288, that added together give a palindrome (30503).

The spelling of 21530288 in words is "twenty-one million, five hundred thirty thousand, two hundred eighty-eight".