21834809 has 4 divisors (see below), whose sum is σ = 21852660. Its totient is φ = 21816960.

The previous prime is 21834803. The next prime is 21834821. The reversal of 21834809 is 90843812.

It is a happy number.

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 19998784 + 1836025 = 4472^2 + 1355^2 .

It is a cyclic number.

It is not a de Polignac number, because 21834809 - 2⁴ = 21834793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21834803) 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, 6944 + ... + 9585.

It is an arithmetic number, because the mean of its divisors is an integer number (5463165).

Almost surely, 2^21834809 is an apocalyptic number.

It is an amenable number.

21834809 is a deficient number, since it is larger than the sum of its proper divisors (17851).

21834809 is a wasteful number, since it uses less digits than its factorization.

21834809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17850.

The product of its (nonzero) digits is 13824, while the sum is 35.

The square root of 21834809 is about 4672.7731594846. The cubic root of 21834809 is about 279.5008496491.

The spelling of 21834809 in words is "twenty-one million, eight hundred thirty-four thousand, eight hundred nine".