861565 has 4 divisors (see below), whose sum is σ = 1033884. Its totient is φ = 689248.

The previous prime is 861563. The next prime is 861571. The reversal of 861565 is 565168.

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 133956 + 727609 = 366^2 + 853^2 .

It is a cyclic number.

It is not a de Polignac number, because 861565 - 2¹ = 861563 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 (861563) 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, 86152 + ... + 86161.

It is an arithmetic number, because the mean of its divisors is an integer number (258471).

2⁸⁶¹⁵⁶⁵ is an apocalyptic number.

It is an amenable number.

861565 is a deficient number, since it is larger than the sum of its proper divisors (172319).

861565 is a wasteful number, since it uses less digits than its factorization.

861565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 172318.

The product of its digits is 7200, while the sum is 31.

The square root of 861565 is about 928.2052574727. The cubic root of 861565 is about 95.1545038946.

The spelling of 861565 in words is "eight hundred sixty-one thousand, five hundred sixty-five".