861665 has 12 divisors (see below), whose sum is σ = 1203156. Its totient is φ = 590688.

The previous prime is 861659. The next prime is 861691. The reversal of 861665 is 566168.

861665 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 614656 + 247009 = 784^2 + 497^2 .

It is not a de Polignac number, because 861665 - 2¹⁰ = 860641 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1514 + ... + 2003.

It is an arithmetic number, because the mean of its divisors is an integer number (100263).

2⁸⁶¹⁶⁶⁵ is an apocalyptic number.

It is an amenable number.

861665 is a deficient number, since it is larger than the sum of its proper divisors (341491).

861665 is a wasteful number, since it uses less digits than its factorization.

861665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3536 (or 3529 counting only the distinct ones).

The product of its digits is 8640, while the sum is 32.

The square root of 861665 is about 928.2591233056. The cubic root of 861665 is about 95.1581852119.

The spelling of 861665 in words is "eight hundred sixty-one thousand, six hundred sixty-five".