21585009 has 4 divisors (see below), whose sum is σ = 28780016. Its totient is φ = 14390004.

The previous prime is 21584999. The next prime is 21585029. The reversal of 21585009 is 90058512.

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 not a de Polignac number, because 21585009 - 2⁷ = 21584881 is a prime.

It is a super-2 number, since 2×21585009² = 931825227060162, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21585029) 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, 3597499 + ... + 3597504.

It is an arithmetic number, because the mean of its divisors is an integer number (7195004).

Almost surely, 2^21585009 is an apocalyptic number.

It is an amenable number.

21585009 is a deficient number, since it is larger than the sum of its proper divisors (7195007).

21585009 is an equidigital number, since it uses as much as digits as its factorization.

21585009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7195006.

The product of its (nonzero) digits is 3600, while the sum is 30.

The square root of 21585009 is about 4645.9669607090. The cubic root of 21585009 is about 278.4308872744.

The spelling of 21585009 in words is "twenty-one million, five hundred eighty-five thousand, nine".