866021 has 4 divisors (see below), whose sum is σ = 932652. Its totient is φ = 799392.

The previous prime is 866011. The next prime is 866029. The reversal of 866021 is 120668.

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

It can be written as a sum of positive squares in 2 ways, for example, as 36100 + 829921 = 190^2 + 911^2 .

It is a cyclic number.

It is not a de Polignac number, because 866021 - 2⁶ = 865957 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (866029) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33296 + ... + 33321.

It is an arithmetic number, because the mean of its divisors is an integer number (233163).

2⁸⁶⁶⁰²¹ is an apocalyptic number.

It is an amenable number.

866021 is a deficient number, since it is larger than the sum of its proper divisors (66631).

866021 is a wasteful number, since it uses less digits than its factorization.

866021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66630.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 866021 is about 930.6024930119. The cubic root of 866021 is about 95.3182677330.

Adding to 866021 its reverse (120668), we get a palindrome (986689).

The spelling of 866021 in words is "eight hundred sixty-six thousand, twenty-one".