21042944 has 36 divisors (see below), whose sum is σ = 45241896. Its totient is φ = 9710592.

The previous prime is 21042919. The next prime is 21042947. The reversal of 21042944 is 44924012.

It is a Harshad number since it is a multiple of its sum of digits (26).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21042947) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 167 + ... + 6489.

Almost surely, 2^21042944 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 21042944, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22620948).

21042944 is an abundant number, since it is smaller than the sum of its proper divisors (24198952).

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

21042944 is an equidigital number, since it uses as much as digits as its factorization.

21042944 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6352 (or 6338 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 26.

The square root of 21042944 is about 4587.2588764969. The cubic root of 21042944 is about 276.0803518762.

Adding to 21042944 its reverse (44924012), we get a palindrome (65966956).

The spelling of 21042944 in words is "twenty-one million, forty-two thousand, nine hundred forty-four".