21594609 has 9 divisors (see below), whose sum is σ = 31212363. Its totient is φ = 14387112.

The previous prime is 21594581. The next prime is 21594613. The reversal of 21594609 is 90649512.

The square root of 21594609 is 4647.

It is a perfect power (a square), and thus also a powerful number.

21594609 is a `hidden beast` number, since 2 + 1 + 594 + 60 + 9 = 666.

It can be written as a sum of positive squares in only one way, i.e., 7306209 + 14288400 = 2703^2 + 3780^2 .

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 21594609 - 2⁷ = 21594481 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21594679) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 13167 + ... + 14715.

Almost surely, 2^21594609 is an apocalyptic number.

21594609 is the 4647-th square number.

21594609 is the 2324-th centered octagonal number.

It is an amenable number.

21594609 is a deficient number, since it is larger than the sum of its proper divisors (9617754).

21594609 is an frugal number, since it uses more digits than its factorization.

21594609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3104 (or 1552 counting only the distinct ones).

The product of its (nonzero) digits is 19440, while the sum is 36.

The cubic root of 21594609 is about 278.4721588247.

Multiplying 21594609 by its sum of digits (36), we get a square (777405924 = 27882²).

The spelling of 21594609 in words is "twenty-one million, five hundred ninety-four thousand, six hundred nine".