811728881 has 4 divisors (see below), whose sum is σ = 812365812. Its totient is φ = 811091952.

The previous prime is 811728877. The next prime is 811728913. The reversal of 811728881 is 188827118.

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

It can be written as a sum of positive squares in 2 ways, for example, as 516198400 + 295530481 = 22720^2 + 17191^2 .

It is a cyclic number.

It is not a de Polignac number, because 811728881 - 2² = 811728877 is a prime.

It is a super-2 number, since 2×811728881² = 1317807552499024322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (811728851) 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, 316550 + ... + 319103.

It is an arithmetic number, because the mean of its divisors is an integer number (203091453).

Almost surely, 2^811728881 is an apocalyptic number.

It is an amenable number.

811728881 is a deficient number, since it is larger than the sum of its proper divisors (636931).

811728881 is a wasteful number, since it uses less digits than its factorization.

811728881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 636930.

The product of its digits is 57344, while the sum is 44.

The square root of 811728881 is about 28490.8560945437. The cubic root of 811728881 is about 932.8324947129.

The spelling of 811728881 in words is "eight hundred eleven million, seven hundred twenty-eight thousand, eight hundred eighty-one".