861665885 has 8 divisors (see below), whose sum is σ = 1039712856. Its totient is φ = 685523520.

The previous prime is 861665851. The next prime is 861665887. The reversal of 861665885 is 588566168.

It can be written as a sum of positive squares in 4 ways, for example, as 1240996 + 860424889 = 1114^2 + 29333^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 861665885 - 2¹⁰ = 861664861 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (861665887) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 475154 + ... + 476963.

It is an arithmetic number, because the mean of its divisors is an integer number (129964107).

Almost surely, 2^861665885 is an apocalyptic number.

It is an amenable number.

861665885 is a deficient number, since it is larger than the sum of its proper divisors (178046971).

861665885 is a wasteful number, since it uses less digits than its factorization.

861665885 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 952303.

The product of its digits is 2764800, while the sum is 53.

The square root of 861665885 is about 29354.1459593019. The cubic root of 861665885 is about 951.5821779027.

The spelling of 861665885 in words is "eight hundred sixty-one million, six hundred sixty-five thousand, eight hundred eighty-five".