21523444 has 12 divisors (see below), whose sum is σ = 37907044. Its totient is φ = 10692864.

The previous prime is 21523433. The next prime is 21523499. The reversal of 21523444 is 44432512.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 13616100 + 7907344 = 3690^2 + 2812^2 .

It is a super-2 number, since 2×21523444² = 926517283242272, which contains 22 as substring.

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 3 ways as a sum of consecutive naturals, for example, 16509 + ... + 17764.

Almost surely, 2^21523444 is an apocalyptic number.

It is an amenable number.

21523444 is a deficient number, since it is larger than the sum of its proper divisors (16383600).

21523444 is a wasteful number, since it uses less digits than its factorization.

21523444 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34434 (or 34432 counting only the distinct ones).

The product of its digits is 3840, while the sum is 25.

The square root of 21523444 is about 4639.3365905052. The cubic root of 21523444 is about 278.1659206550.

Adding to 21523444 its reverse (44432512), we get a palindrome (65955956).

The spelling of 21523444 in words is "twenty-one million, five hundred twenty-three thousand, four hundred forty-four".