20811816 has 40 divisors (see below), whose sum is σ = 58294170. Its totient is φ = 6937056.

The previous prime is 20811811. The next prime is 20811823. The reversal of 20811816 is 61811802.

It can be written as a sum of positive squares in only one way, i.e., 20738916 + 72900 = 4554^2 + 270^2 .

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a zygodrome in base 3.

It is a self number, because there is not a number n which added to its sum of digits gives 20811816.

It is not an unprimeable number, because it can be changed into a prime (20811811) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 15411 + ... + 16706.

Almost surely, 2^20811816 is an apocalyptic number.

It is an amenable number.

20811816 is an abundant number, since it is smaller than the sum of its proper divisors (37482354).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20811816 is a wasteful number, since it uses less digits than its factorization.

20811816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32135 (or 32122 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 27.

The square root of 20811816 is about 4561.9969311695. The cubic root of 20811816 is about 275.0658398829.

The spelling of 20811816 in words is "twenty million, eight hundred eleven thousand, eight hundred sixteen".