811511561 has 4 divisors (see below), whose sum is σ = 927441792. Its totient is φ = 695581332.

The previous prime is 811511551. The next prime is 811511579. The reversal of 811511561 is 165115118.

811511561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 811511561 - 2⁶ = 811511497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (811511531) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 57965105 + ... + 57965118.

It is an arithmetic number, because the mean of its divisors is an integer number (231860448).

Almost surely, 2^811511561 is an apocalyptic number.

It is an amenable number.

811511561 is a deficient number, since it is larger than the sum of its proper divisors (115930231).

811511561 is a wasteful number, since it uses less digits than its factorization.

811511561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 115930230.

The product of its digits is 1200, while the sum is 29.

The square root of 811511561 is about 28487.0419840320. The cubic root of 811511561 is about 932.7492398000.

Adding to 811511561 its reverse (165115118), we get a palindrome (976626679).

The spelling of 811511561 in words is "eight hundred eleven million, five hundred eleven thousand, five hundred sixty-one".