21440244 has 48 divisors (see below), whose sum is σ = 58352000. Its totient is φ = 6124608.

The previous prime is 21440239. The next prime is 21440257. The reversal of 21440244 is 44204412.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a zygodrome in base 11.

It is a self number, because there is not a number n which added to its sum of digits gives 21440244.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1512 + ... + 6720.

Almost surely, 2^21440244 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 21440244, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29176000).

21440244 is an abundant number, since it is smaller than the sum of its proper divisors (36911756).

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

21440244 is a wasteful number, since it uses less digits than its factorization.

21440244 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5237 (or 5221 counting only the distinct ones).

The product of its (nonzero) digits is 1024, while the sum is 21.

The square root of 21440244 is about 4630.3611090281. The cubic root of 21440244 is about 277.8070361833.

Adding to 21440244 its reverse (44204412), we get a palindrome (65644656).

The spelling of 21440244 in words is "twenty-one million, four hundred forty thousand, two hundred forty-four".