21409809 has 8 divisors (see below), whose sum is σ = 29467392. Its totient is φ = 13812720.

The previous prime is 21409807. The next prime is 21409819. The reversal of 21409809 is 90890412.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21409809 - 2¹ = 21409807 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21409809.

It is not an unprimeable number, because it can be changed into a prime (21409807) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 115014 + ... + 115199.

It is an arithmetic number, because the mean of its divisors is an integer number (3683424).

Almost surely, 2^21409809 is an apocalyptic number.

It is an amenable number.

21409809 is a deficient number, since it is larger than the sum of its proper divisors (8057583).

21409809 is a wasteful number, since it uses less digits than its factorization.

21409809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 230247.

The product of its (nonzero) digits is 5184, while the sum is 33.

The square root of 21409809 is about 4627.0734811542. The cubic root of 21409809 is about 277.6755224276.

The spelling of 21409809 in words is "twenty-one million, four hundred nine thousand, eight hundred nine".