21039591 has 16 divisors (see below), whose sum is σ = 30016224. Its totient is φ = 13062144.

The previous prime is 21039589. The next prime is 21039611. The reversal of 21039591 is 19593012.

It is not a de Polignac number, because 21039591 - 2¹ = 21039589 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21039521) 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, 2821 + ... + 7073.

It is an arithmetic number, because the mean of its divisors is an integer number (1876014).

Almost surely, 2^21039591 is an apocalyptic number.

21039591 is a deficient number, since it is larger than the sum of its proper divisors (8976633).

21039591 is a wasteful number, since it uses less digits than its factorization.

21039591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4370.

The product of its (nonzero) digits is 2430, while the sum is 30.

The square root of 21039591 is about 4586.8933931366. The cubic root of 21039591 is about 276.0656874739.

The spelling of 21039591 in words is "twenty-one million, thirty-nine thousand, five hundred ninety-one".