21520444 has 12 divisors (see below), whose sum is σ = 41084568. Its totient is φ = 9782000.

The previous prime is 21520441. The next prime is 21520451. The reversal of 21520444 is 44402512.

It is a happy number.

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

It is a zygodrome in base 3.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21520441) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 244507 + ... + 244594.

It is an arithmetic number, because the mean of its divisors is an integer number (3423714).

Almost surely, 2^21520444 is an apocalyptic number.

It is an amenable number.

21520444 is a deficient number, since it is larger than the sum of its proper divisors (19564124).

21520444 is a wasteful number, since it uses less digits than its factorization.

21520444 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 489116 (or 489114 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 22.

The square root of 21520444 is about 4639.0132571486. The cubic root of 21520444 is about 278.1529961971.

Adding to 21520444 its reverse (44402512), we get a palindrome (65922956).

The spelling of 21520444 in words is "twenty-one million, five hundred twenty thousand, four hundred forty-four".