21839409 has 8 divisors (see below), whose sum is σ = 32354720. Its totient is φ = 14559588.

The previous prime is 21839401. The next prime is 21839431. The reversal of 21839409 is 90493812.

21839409 is a `hidden beast` number, since 218 + 39 + 409 = 666.

It is not a de Polignac number, because 21839409 - 2³ = 21839401 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21839401) 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 7 ways as a sum of consecutive naturals, for example, 404407 + ... + 404460.

It is an arithmetic number, because the mean of its divisors is an integer number (4044340).

Almost surely, 2^21839409 is an apocalyptic number.

It is an amenable number.

21839409 is a deficient number, since it is larger than the sum of its proper divisors (10515311).

21839409 is an equidigital number, since it uses as much as digits as its factorization.

21839409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 808876 (or 808870 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 36.

The square root of 21839409 is about 4673.2653466286. The cubic root of 21839409 is about 279.5204760116.

The spelling of 21839409 in words is "twenty-one million, eight hundred thirty-nine thousand, four hundred nine".