21808089 has 8 divisors (see below), whose sum is σ = 32308320. Its totient is φ = 14538708.

The previous prime is 21808081. The next prime is 21808091. The reversal of 21808089 is 98080812.

It is not a de Polignac number, because 21808089 - 2³ = 21808081 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21808081) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 403827 + ... + 403880.

It is an arithmetic number, because the mean of its divisors is an integer number (4038540).

Almost surely, 2^21808089 is an apocalyptic number.

It is an amenable number.

21808089 is a deficient number, since it is larger than the sum of its proper divisors (10500231).

21808089 is an equidigital number, since it uses as much as digits as its factorization.

21808089 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 807716 (or 807710 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 36.

The square root of 21808089 is about 4669.9131683576. The cubic root of 21808089 is about 279.3867915387.

The spelling of 21808089 in words is "twenty-one million, eight hundred eight thousand, eighty-nine".