865521 has 12 divisors (see below), whose sum is σ = 1323972. Its totient is φ = 542976.

The previous prime is 865511. The next prime is 865537. The reversal of 865521 is 125568.

865521 is a `hidden beast` number, since 8 + 655 + 2 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 360000 + 505521 = 600^2 + 711^2 .

It is not a de Polignac number, because 865521 - 2⁶ = 865457 is a prime.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (865511) 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 11 ways as a sum of consecutive naturals, for example, 2676 + ... + 2981.

It is an arithmetic number, because the mean of its divisors is an integer number (110331).

2⁸⁶⁵⁵²¹ is an apocalyptic number.

It is an amenable number.

865521 is a deficient number, since it is larger than the sum of its proper divisors (458451).

865521 is a wasteful number, since it uses less digits than its factorization.

865521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5680 (or 5677 counting only the distinct ones).

The product of its digits is 2400, while the sum is 27.

The square root of 865521 is about 930.3338110592. Note that the first 3 decimals coincide. The cubic root of 865521 is about 95.2999200991.

The spelling of 865521 in words is "eight hundred sixty-five thousand, five hundred twenty-one".