21320244 has 72 divisors (see below), whose sum is σ = 62270208. Its totient is φ = 6078720.

The previous prime is 21320239. The next prime is 21320267. The reversal of 21320244 is 44202312.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5149 + ... + 8315.

It is an arithmetic number, because the mean of its divisors is an integer number (864864).

Almost surely, 2^21320244 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 21320244, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31135104).

21320244 is an abundant number, since it is smaller than the sum of its proper divisors (40949964).

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

21320244 is a wasteful number, since it uses less digits than its factorization.

21320244 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3205 (or 3200 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 21320244 is about 4617.3849742035. The cubic root of 21320244 is about 277.2877754051.

Adding to 21320244 its reverse (44202312), we get a palindrome (65522556).

The spelling of 21320244 in words is "twenty-one million, three hundred twenty thousand, two hundred forty-four".