21058493 has 4 divisors (see below), whose sum is σ = 21070428. Its totient is φ = 21046560.

The previous prime is 21058487. The next prime is 21058523. The reversal of 21058493 is 39485012.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 4761124 + 16297369 = 2182^2 + 4037^2 .

It is a cyclic number.

It is not a de Polignac number, because 21058493 - 2²⁰ = 20009917 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 (21058463) 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, 2738 + ... + 7043.

It is an arithmetic number, because the mean of its divisors is an integer number (5267607).

Almost surely, 2^21058493 is an apocalyptic number.

It is an amenable number.

21058493 is a deficient number, since it is larger than the sum of its proper divisors (11935).

21058493 is an equidigital number, since it uses as much as digits as its factorization.

21058493 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11934.

The product of its (nonzero) digits is 8640, while the sum is 32.

The square root of 21058493 is about 4588.9533665096. The cubic root of 21058493 is about 276.1483353372.

The spelling of 21058493 in words is "twenty-one million, fifty-eight thousand, four hundred ninety-three".