866509 has 4 divisors (see below), whose sum is σ = 990304. Its totient is φ = 742716.

The previous prime is 866477. The next prime is 866513. The reversal of 866509 is 905668.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 866509 - 2⁵ = 866477 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (866519) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 61887 + ... + 61900.

It is an arithmetic number, because the mean of its divisors is an integer number (247576).

2⁸⁶⁶⁵⁰⁹ is an apocalyptic number.

It is an amenable number.

866509 is a deficient number, since it is larger than the sum of its proper divisors (123795).

866509 is a wasteful number, since it uses less digits than its factorization.

866509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 123794.

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 866509 is about 930.8646518157. The cubic root of 866509 is about 95.3361682152.

The spelling of 866509 in words is "eight hundred sixty-six thousand, five hundred nine".