861311808 has 126 divisors (see below), whose sum is σ = 2871957426. Its totient is φ = 246081024.

The previous prime is 861311807. The next prime is 861311821. The reversal of 861311808 is 808113168.

It can be written as a sum of positive squares in only one way, i.e., 448084224 + 413227584 = 21168^2 + 20328^2 .

It is a tau number, because it is divible by the number of its divisors (126).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (861311807) 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 17 ways as a sum of consecutive naturals, for example, 12966 + ... + 43482.

Almost surely, 2^861311808 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 861311808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1435978713).

861311808 is an abundant number, since it is smaller than the sum of its proper divisors (2010645618).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

861311808 is a wasteful number, since it uses less digits than its factorization.

861311808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30549 (or 30529 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 36.

The square root of 861311808 is about 29348.1142153972. The cubic root of 861311808 is about 951.4518182006.

The spelling of 861311808 in words is "eight hundred sixty-one million, three hundred eleven thousand, eight hundred eight".