865531 has 4 divisors (see below), whose sum is σ = 874552. Its totient is φ = 856512.

The previous prime is 865511. The next prime is 865537. The reversal of 865531 is 135568.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 865531 - 2⁵ = 865499 is a prime.

It is a super-2 number, since 2×865531² = 1498287823922, which contains 22 as substring.

865531 is a lucky number.

It is a nialpdrome in base 10.

It is a self number, because there is not a number n which added to its sum of digits gives 865531.

It is not an unprimeable number, because it can be changed into a prime (865537) 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 3 ways as a sum of consecutive naturals, for example, 4365 + ... + 4558.

It is an arithmetic number, because the mean of its divisors is an integer number (218638).

2⁸⁶⁵⁵³¹ is an apocalyptic number.

865531 is a deficient number, since it is larger than the sum of its proper divisors (9021).

865531 is an equidigital number, since it uses as much as digits as its factorization.

865531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9020.

The product of its digits is 3600, while the sum is 28.

The square root of 865531 is about 930.3391854587. The cubic root of 865531 is about 95.3002871210.

The spelling of 865531 in words is "eight hundred sixty-five thousand, five hundred thirty-one".