20644021 has 4 divisors (see below), whose sum is σ = 20659392. Its totient is φ = 20628652.

The previous prime is 20644007. The next prime is 20644037. The reversal of 20644021 is 12044602.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20644021 - 2⁷ = 20643893 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 20644021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20644081) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5455 + ... + 8428.

It is an arithmetic number, because the mean of its divisors is an integer number (5164848).

Almost surely, 2^20644021 is an apocalyptic number.

It is an amenable number.

20644021 is a deficient number, since it is larger than the sum of its proper divisors (15371).

20644021 is a wasteful number, since it uses less digits than its factorization.

20644021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15370.

The product of its (nonzero) digits is 384, while the sum is 19.

The square root of 20644021 is about 4543.5691917258. The cubic root of 20644021 is about 274.3246059657.

Adding to 20644021 its reverse (12044602), we get a palindrome (32688623).

The spelling of 20644021 in words is "twenty million, six hundred forty-four thousand, twenty-one".