20618809 has 4 divisors (see below), whose sum is σ = 20638800. Its totient is φ = 20598820.

The previous prime is 20618791. The next prime is 20618821. The reversal of 20618809 is 90881602.

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 20618809 - 2¹³ = 20610617 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20618209) 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, 8359 + ... + 10540.

It is an arithmetic number, because the mean of its divisors is an integer number (5159700).

Almost surely, 2^20618809 is an apocalyptic number.

It is an amenable number.

20618809 is a deficient number, since it is larger than the sum of its proper divisors (19991).

20618809 is a wasteful number, since it uses less digits than its factorization.

20618809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19990.

The product of its (nonzero) digits is 6912, while the sum is 34.

The square root of 20618809 is about 4540.7938733222. The cubic root of 20618809 is about 274.2128853303.

The spelling of 20618809 in words is "twenty million, six hundred eighteen thousand, eight hundred nine".