20811523 has 4 divisors (see below), whose sum is σ = 21075040. Its totient is φ = 20548008.

The previous prime is 20811521. The next prime is 20811541. The reversal of 20811523 is 32511802.

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 20811523 - 2¹ = 20811521 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20811494 and 20811503.

It is not an unprimeable number, because it can be changed into a prime (20811521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 131640 + ... + 131797.

It is an arithmetic number, because the mean of its divisors is an integer number (5268760).

Almost surely, 2^20811523 is an apocalyptic number.

20811523 is a deficient number, since it is larger than the sum of its proper divisors (263517).

20811523 is an equidigital number, since it uses as much as digits as its factorization.

20811523 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 263516.

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 20811523 is about 4561.9648179266. The cubic root of 20811523 is about 275.0645490349.

The spelling of 20811523 in words is "twenty million, eight hundred eleven thousand, five hundred twenty-three".