21544609 has 4 divisors (see below), whose sum is σ = 21657600. Its totient is φ = 21431620.

The previous prime is 21544571. The next prime is 21544631. The reversal of 21544609 is 90644512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21544609 - 2⁹ = 21544097 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21544669) 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, 56209 + ... + 56590.

It is an arithmetic number, because the mean of its divisors is an integer number (5414400).

Almost surely, 2^21544609 is an apocalyptic number.

It is an amenable number.

21544609 is a deficient number, since it is larger than the sum of its proper divisors (112991).

21544609 is a wasteful number, since it uses less digits than its factorization.

21544609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 112990.

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 21544609 is about 4641.6170673592. The cubic root of 21544609 is about 278.2570685987.

The spelling of 21544609 in words is "twenty-one million, five hundred forty-four thousand, six hundred nine".