21044591 has 4 divisors (see below), whose sum is σ = 21062184. Its totient is φ = 21027000.

The previous prime is 21044581. The next prime is 21044627. The reversal of 21044591 is 19544012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21044591 - 2¹⁰ = 21043567 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21044591.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21044531) 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 3 ways as a sum of consecutive naturals, for example, 6860 + ... + 9441.

It is an arithmetic number, because the mean of its divisors is an integer number (5265546).

Almost surely, 2^21044591 is an apocalyptic number.

21044591 is a deficient number, since it is larger than the sum of its proper divisors (17593).

21044591 is a wasteful number, since it uses less digits than its factorization.

21044591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17592.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 21044591 is about 4587.4383919569. The cubic root of 21044591 is about 276.0875544881.

The spelling of 21044591 in words is "twenty-one million, forty-four thousand, five hundred ninety-one".