865561 has 8 divisors (see below), whose sum is σ = 895104. Its totient is φ = 836640.

The previous prime is 865537. The next prime is 865577. The reversal of 865561 is 165568.

865561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is a cyclic number.

It is not a de Polignac number, because 865561 - 2⁹ = 865049 is a prime.

It is a Duffinian number.

865561 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (865511) 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, 5100 + ... + 5266.

It is an arithmetic number, because the mean of its divisors is an integer number (111888).

2⁸⁶⁵⁵⁶¹ is an apocalyptic number.

It is an amenable number.

865561 is a deficient number, since it is larger than the sum of its proper divisors (29543).

865561 is a wasteful number, since it uses less digits than its factorization.

865561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 311.

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

The square root of 865561 is about 930.3553084709. The cubic root of 865561 is about 95.3013881698.

The spelling of 865561 in words is "eight hundred sixty-five thousand, five hundred sixty-one".