811561819 has 4 divisors (see below), whose sum is σ = 818743896. Its totient is φ = 804379744.

The previous prime is 811561787. The next prime is 811561847. The reversal of 811561819 is 918165118.

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 811561819 - 2⁵ = 811561787 is a prime.

It is a super-2 number, since 2×811561819² = 1317265172117177522, which contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (811561859) 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, 3590869 + ... + 3591094.

It is an arithmetic number, because the mean of its divisors is an integer number (204685974).

Almost surely, 2^811561819 is an apocalyptic number.

811561819 is a deficient number, since it is larger than the sum of its proper divisors (7182077).

811561819 is a wasteful number, since it uses less digits than its factorization.

811561819 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7182076.

The product of its digits is 17280, while the sum is 40.

The square root of 811561819 is about 28487.9240907441. The cubic root of 811561819 is about 932.7684948732.

The spelling of 811561819 in words is "eight hundred eleven million, five hundred sixty-one thousand, eight hundred nineteen".