20475821 has 4 divisors (see below), whose sum is σ = 20515644. Its totient is φ = 20436000.

The previous prime is 20475817. The next prime is 20475839. The reversal of 20475821 is 12857402.

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

It can be written as a sum of positive squares in 2 ways, for example, as 5929225 + 14546596 = 2435^2 + 3814^2 .

It is a cyclic number.

It is not a de Polignac number, because 20475821 - 2² = 20475817 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20475881) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19130 + ... + 20171.

It is an arithmetic number, because the mean of its divisors is an integer number (5128911).

Almost surely, 2^20475821 is an apocalyptic number.

It is an amenable number.

20475821 is a deficient number, since it is larger than the sum of its proper divisors (39823).

20475821 is an equidigital number, since it uses as much as digits as its factorization.

20475821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39822.

The product of its (nonzero) digits is 4480, while the sum is 29.

The square root of 20475821 is about 4525.0216574067. The cubic root of 20475821 is about 273.5775408548.

The spelling of 20475821 in words is "twenty million, four hundred seventy-five thousand, eight hundred twenty-one".