21090839 has 16 divisors (see below), whose sum is σ = 27440640. Its totient is φ = 15718560.

The previous prime is 21090833. The next prime is 21090841. The reversal of 21090839 is 93809012.

It is not a de Polignac number, because 21090839 - 2⁸ = 21090583 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21090833) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4184 + ... + 7725.

It is an arithmetic number, because the mean of its divisors is an integer number (1715040).

Almost surely, 2^21090839 is an apocalyptic number.

21090839 is a deficient number, since it is larger than the sum of its proper divisors (6349801).

21090839 is a wasteful number, since it uses less digits than its factorization.

21090839 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11950.

The product of its (nonzero) digits is 3888, while the sum is 32.

The square root of 21090839 is about 4592.4763472445. The cubic root of 21090839 is about 276.2896516317.

The spelling of 21090839 in words is "twenty-one million, ninety thousand, eight hundred thirty-nine".