20558021 has 24 divisors (see below), whose sum is σ = 24131520. Its totient is φ = 17462720.

The previous prime is 20558009. The next prime is 20558029. The reversal of 20558021 is 12085502.

It is not a de Polignac number, because 20558021 - 2¹⁴ = 20541637 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20558029) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 230945 + ... + 231033.

It is an arithmetic number, because the mean of its divisors is an integer number (1005480).

Almost surely, 2^20558021 is an apocalyptic number.

It is an amenable number.

20558021 is a deficient number, since it is larger than the sum of its proper divisors (3573499).

20558021 is a wasteful number, since it uses less digits than its factorization.

20558021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 217 (or 206 counting only the distinct ones).

The product of its (nonzero) digits is 800, while the sum is 23.

The square root of 20558021 is about 4534.0953893803. The cubic root of 20558021 is about 273.9431435831.

The spelling of 20558021 in words is "twenty million, five hundred fifty-eight thousand, twenty-one".