20808781 has 32 divisors (see below), whose sum is σ = 26624000. Its totient is φ = 16193520.

The previous prime is 20808779. The next prime is 20808787. The reversal of 20808781 is 18780802.

It is not a de Polignac number, because 20808781 - 2¹ = 20808779 is a prime.

It is a super-2 number, since 2×20808781² = 866010733411922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20808787) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 201976 + ... + 202078.

It is an arithmetic number, because the mean of its divisors is an integer number (832000).

Almost surely, 2^20808781 is an apocalyptic number.

It is an amenable number.

20808781 is a deficient number, since it is larger than the sum of its proper divisors (5815219).

20808781 is a wasteful number, since it uses less digits than its factorization.

20808781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 174 (or 160 counting only the distinct ones).

The product of its (nonzero) digits is 7168, while the sum is 34.

The square root of 20808781 is about 4561.6642796243. The cubic root of 20808781 is about 275.0524682257.

The spelling of 20808781 in words is "twenty million, eight hundred eight thousand, seven hundred eighty-one".