21332809 has 4 divisors (see below), whose sum is σ = 21355204. Its totient is φ = 21310416.

The previous prime is 21332797. The next prime is 21332813. The reversal of 21332809 is 90823312.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 19998784 + 1334025 = 4472^2 + 1155^2 .

It is a cyclic number.

It is not a de Polignac number, because 21332809 - 2¹¹ = 21330761 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21332819) 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, 9702 + ... + 11695.

It is an arithmetic number, because the mean of its divisors is an integer number (5338801).

Almost surely, 2^21332809 is an apocalyptic number.

It is an amenable number.

21332809 is a deficient number, since it is larger than the sum of its proper divisors (22395).

21332809 is an equidigital number, since it uses as much as digits as its factorization.

21332809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22394.

The product of its (nonzero) digits is 2592, while the sum is 28.

The square root of 21332809 is about 4618.7453924199. The cubic root of 21332809 is about 277.3422375190.

The spelling of 21332809 in words is "twenty-one million, three hundred thirty-two thousand, eight hundred nine".