20855509 has 4 divisors (see below), whose sum is σ = 20912704. Its totient is φ = 20798316.

The previous prime is 20855501. The next prime is 20855519. The reversal of 20855509 is 90555802.

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 20855509 - 2³ = 20855501 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 (20855501) 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, 28047 + ... + 28780.

It is an arithmetic number, because the mean of its divisors is an integer number (5228176).

Almost surely, 2^20855509 is an apocalyptic number.

It is an amenable number.

20855509 is a deficient number, since it is larger than the sum of its proper divisors (57195).

20855509 is an equidigital number, since it uses as much as digits as its factorization.

20855509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57194.

The product of its (nonzero) digits is 18000, while the sum is 34.

The square root of 20855509 is about 4566.7832223568. The cubic root of 20855509 is about 275.2581993723.

The spelling of 20855509 in words is "twenty million, eight hundred fifty-five thousand, five hundred nine".