21531844 has 6 divisors (see below), whose sum is σ = 37680734. Its totient is φ = 10765920.

The previous prime is 21531827. The next prime is 21531871. The reversal of 21531844 is 44813512.

It can be written as a sum of positive squares in only one way, i.e., 10969344 + 10562500 = 3312^2 + 3250^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2691477 + ... + 2691484.

Almost surely, 2^21531844 is an apocalyptic number.

It is an amenable number.

21531844 is a deficient number, since it is larger than the sum of its proper divisors (16148890).

21531844 is a wasteful number, since it uses less digits than its factorization.

21531844 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5382965 (or 5382963 counting only the distinct ones).

The product of its digits is 3840, while the sum is 28.

The square root of 21531844 is about 4640.2418040443. The cubic root of 21531844 is about 278.2021027491.

The spelling of 21531844 in words is "twenty-one million, five hundred thirty-one thousand, eight hundred forty-four".