20813811 has 4 divisors (see below), whose sum is σ = 27751752. Its totient is φ = 13875872.

The previous prime is 20813791. The next prime is 20813813. The reversal of 20813811 is 11831802.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20813811 - 2¹⁹ = 20289523 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20813813) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3468966 + ... + 3468971.

It is an arithmetic number, because the mean of its divisors is an integer number (6937938).

Almost surely, 2^20813811 is an apocalyptic number.

20813811 is a deficient number, since it is larger than the sum of its proper divisors (6937941).

20813811 is an equidigital number, since it uses as much as digits as its factorization.

20813811 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6937940.

The product of its (nonzero) digits is 384, while the sum is 24.

The square root of 20813811 is about 4562.2155801759. The cubic root of 20813811 is about 275.0746287814.

Subtracting from 20813811 its reverse (11831802), we obtain a square (8982009 = 2997²).

The spelling of 20813811 in words is "twenty million, eight hundred thirteen thousand, eight hundred eleven".