21318544 has 40 divisors (see below), whose sum is σ = 47106360. Its totient is φ = 9259008.

The previous prime is 21318541. The next prime is 21318599. The reversal of 21318544 is 44581312.

It can be written as a sum of positive squares in 4 ways, for example, as 6969600 + 14348944 = 2640^2 + 3788^2 .

It is not an unprimeable number, because it can be changed into a prime (21318541) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 522 + ... + 6550.

It is an arithmetic number, because the mean of its divisors is an integer number (1177659).

Almost surely, 2^21318544 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 21318544, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23553180).

21318544 is an abundant number, since it is smaller than the sum of its proper divisors (25787816).

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

21318544 is a wasteful number, since it uses less digits than its factorization.

21318544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6067 (or 6061 counting only the distinct ones).

The product of its digits is 3840, while the sum is 28.

The square root of 21318544 is about 4617.2008836523. The cubic root of 21318544 is about 277.2804052307.

Adding to 21318544 its reverse (44581312), we get a palindrome (65899856).

The spelling of 21318544 in words is "twenty-one million, three hundred eighteen thousand, five hundred forty-four".