21557089 has 4 divisors (see below), whose sum is σ = 21586324. Its totient is φ = 21527856.

The previous prime is 21557057. The next prime is 21557099. The reversal of 21557089 is 98075512.

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 11444689 + 10112400 = 3383^2 + 3180^2 .

It is a cyclic number.

It is not a de Polignac number, because 21557089 - 2⁵ = 21557057 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21557099) 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 3 ways as a sum of consecutive naturals, for example, 13482 + ... + 14995.

It is an arithmetic number, because the mean of its divisors is an integer number (5396581).

Almost surely, 2^21557089 is an apocalyptic number.

It is an amenable number.

21557089 is a deficient number, since it is larger than the sum of its proper divisors (29235).

21557089 is an equidigital number, since it uses as much as digits as its factorization.

21557089 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29234.

The product of its (nonzero) digits is 25200, while the sum is 37.

The square root of 21557089 is about 4642.9612318002. The cubic root of 21557089 is about 278.3107862581.

The spelling of 21557089 in words is "twenty-one million, five hundred fifty-seven thousand, eighty-nine".