866639 has 2 divisors, whose sum is σ = 866640. Its totient is φ = 866638.

The previous prime is 866629. The next prime is 866641. The reversal of 866639 is 936668.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 866639 - 2⁴ = 866623 is a prime.

It is a Sophie Germain prime.

Together with 866641, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 866639.

It is not a weakly prime, because it can be changed into another prime (866629) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 433319 + 433320.

It is an arithmetic number, because the mean of its divisors is an integer number (433320).

2⁸⁶⁶⁶³⁹ is an apocalyptic number.

866639 is a deficient number, since it is larger than the sum of its proper divisors (1).

866639 is an equidigital number, since it uses as much as digits as its factorization.

866639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 46656, while the sum is 38.

The square root of 866639 is about 930.9344767490. The cubic root of 866639 is about 95.3409356525.

The spelling of 866639 in words is "eight hundred sixty-six thousand, six hundred thirty-nine".