866581 has 2 divisors, whose sum is σ = 866582. Its totient is φ = 866580.

The previous prime is 866573. The next prime is 866623. The reversal of 866581 is 185668.

It is a happy number.

866581 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 864900 + 1681 = 930^2 + 41^2 .

It is a cyclic number.

It is not a de Polignac number, because 866581 - 2³ = 866573 is a prime.

It is a super-2 number, since 2×866581² = 1501925259122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (866081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 433290 + 433291.

It is an arithmetic number, because the mean of its divisors is an integer number (433291).

2⁸⁶⁶⁵⁸¹ is an apocalyptic number.

It is an amenable number.

866581 is a deficient number, since it is larger than the sum of its proper divisors (1).

866581 is an equidigital number, since it uses as much as digits as its factorization.

866581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 11520, while the sum is 34.

The square root of 866581 is about 930.9033247336. The cubic root of 866581 is about 95.3388087009.

The spelling of 866581 in words is "eight hundred sixty-six thousand, five hundred eighty-one".