21839905 has 4 divisors (see below), whose sum is σ = 26207892. Its totient is φ = 17471920.

The previous prime is 21839893. The next prime is 21839933. The reversal of 21839905 is 50993812.

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 8363664 + 13476241 = 2892^2 + 3671^2 .

It is not a de Polignac number, because 21839905 - 2⁷ = 21839777 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2183986 + ... + 2183995.

It is an arithmetic number, because the mean of its divisors is an integer number (6551973).

Almost surely, 2^21839905 is an apocalyptic number.

It is an amenable number.

21839905 is a deficient number, since it is larger than the sum of its proper divisors (4367987).

21839905 is an equidigital number, since it uses as much as digits as its factorization.

21839905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4367986.

The product of its (nonzero) digits is 19440, while the sum is 37.

The square root of 21839905 is about 4673.3184141464. The cubic root of 21839905 is about 279.5225920809.

The spelling of 21839905 in words is "twenty-one million, eight hundred thirty-nine thousand, nine hundred five".