20566421 has 4 divisors (see below), whose sum is σ = 20575500. Its totient is φ = 20557344.

The previous prime is 20566409. The next prime is 20566453. The reversal of 20566421 is 12466502.

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 442225 + 20124196 = 665^2 + 4486^2 .

It is a cyclic number.

It is not a de Polignac number, because 20566421 - 2¹⁴ = 20550037 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 (20566121) 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, 1985 + ... + 6713.

It is an arithmetic number, because the mean of its divisors is an integer number (5143875).

Almost surely, 2^20566421 is an apocalyptic number.

It is an amenable number.

20566421 is a deficient number, since it is larger than the sum of its proper divisors (9079).

20566421 is an equidigital number, since it uses as much as digits as its factorization.

20566421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9078.

The product of its (nonzero) digits is 2880, while the sum is 26.

The square root of 20566421 is about 4535.0216096508. The cubic root of 20566421 is about 273.9804495259.

The spelling of 20566421 in words is "twenty million, five hundred sixty-six thousand, four hundred twenty-one".