20388639 has 4 divisors (see below), whose sum is σ = 27184856. Its totient is φ = 13592424.

The previous prime is 20388583. The next prime is 20388727. The reversal of 20388639 is 93688302.

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

It is not a de Polignac number, because 20388639 - 2⁹ = 20388127 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20388597 and 20388606.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20388839) 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, 3398104 + ... + 3398109.

It is an arithmetic number, because the mean of its divisors is an integer number (6796214).

Almost surely, 2^20388639 is an apocalyptic number.

20388639 is a deficient number, since it is larger than the sum of its proper divisors (6796217).

20388639 is an equidigital number, since it uses as much as digits as its factorization.

20388639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6796216.

The product of its (nonzero) digits is 62208, while the sum is 39.

The square root of 20388639 is about 4515.3780572617. The cubic root of 20388639 is about 273.1887087705.

The spelling of 20388639 in words is "twenty million, three hundred eighty-eight thousand, six hundred thirty-nine".