866621 has 4 divisors (see below), whose sum is σ = 990432. Its totient is φ = 742812.

The previous prime is 866581. The next prime is 866623. The reversal of 866621 is 126668.

866621 is nontrivially palindromic in base 16.

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 not a de Polignac number, because 866621 - 2¹⁰ = 865597 is a prime.

It is a Duffinian number.

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 (866623) 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, 61895 + ... + 61908.

It is an arithmetic number, because the mean of its divisors is an integer number (247608).

2⁸⁶⁶⁶²¹ is an apocalyptic number.

It is an amenable number.

866621 is a deficient number, since it is larger than the sum of its proper divisors (123811).

866621 is a wasteful number, since it uses less digits than its factorization.

866621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 123810.

The product of its digits is 3456, while the sum is 29.

The square root of 866621 is about 930.9248089937. The cubic root of 866621 is about 95.3402755742.

The spelling of 866621 in words is "eight hundred sixty-six thousand, six hundred twenty-one".