20902809 has 16 divisors (see below), whose sum is σ = 29998080. Its totient is φ = 12898560.

The previous prime is 20902801. The next prime is 20902811. The reversal of 20902809 is 90820902.

It is not a de Polignac number, because 20902809 - 2³ = 20902801 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20902801) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 249 + ... + 6470.

It is an arithmetic number, because the mean of its divisors is an integer number (1874880).

Almost surely, 2^20902809 is an apocalyptic number.

It is an amenable number.

20902809 is a deficient number, since it is larger than the sum of its proper divisors (9095271).

20902809 is a wasteful number, since it uses less digits than its factorization.

20902809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6800.

The product of its (nonzero) digits is 2592, while the sum is 30.

The square root of 20902809 is about 4571.9589893174. The cubic root of 20902809 is about 275.4661361556.

The spelling of 20902809 in words is "twenty million, nine hundred two thousand, eight hundred nine".