21634809 has 16 divisors (see below), whose sum is σ = 33509760. Its totient is φ = 12159360.

The previous prime is 21634801. The next prime is 21634813. The reversal of 21634809 is 90843612.

It is not a de Polignac number, because 21634809 - 2³ = 21634801 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21634809.

It is not an unprimeable number, because it can be changed into a prime (21634801) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7164 + ... + 9725.

It is an arithmetic number, because the mean of its divisors is an integer number (2094360).

Almost surely, 2^21634809 is an apocalyptic number.

It is an amenable number.

21634809 is a deficient number, since it is larger than the sum of its proper divisors (11874951).

21634809 is a wasteful number, since it uses less digits than its factorization.

21634809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16960.

The product of its (nonzero) digits is 10368, while the sum is 33.

The square root of 21634809 is about 4651.3233600772. The cubic root of 21634809 is about 278.6448507134.

The spelling of 21634809 in words is "twenty-one million, six hundred thirty-four thousand, eight hundred nine".