21530344 has 64 divisors (see below), whose sum is σ = 47232000. Its totient is φ = 9097920.

The previous prime is 21530329. The next prime is 21530387. The reversal of 21530344 is 44303512.

It is a Harshad number since it is a multiple of its sum of digits (22).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 132007 + ... + 132169.

It is an arithmetic number, because the mean of its divisors is an integer number (738000).

Almost surely, 2^21530344 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 21530344, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23616000).

21530344 is an abundant number, since it is smaller than the sum of its proper divisors (25701656).

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

21530344 is a wasteful number, since it uses less digits than its factorization.

21530344 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 278 (or 274 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 22.

The square root of 21530344 is about 4640.0801717212. The cubic root of 21530344 is about 278.1956423511.

Adding to 21530344 its reverse (44303512), we get a palindrome (65833856).

The spelling of 21530344 in words is "twenty-one million, five hundred thirty thousand, three hundred forty-four".