856639 has 8 divisors (see below), whose sum is σ = 997920. Its totient is φ = 720096.

The previous prime is 856637. The next prime is 856649. The reversal of 856639 is 936658.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 856639 - 2¹ = 856637 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 856598 and 856607.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (856637) 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 7 ways as a sum of consecutive naturals, for example, 784 + ... + 1525.

It is an arithmetic number, because the mean of its divisors is an integer number (124740).

2⁸⁵⁶⁶³⁹ is an apocalyptic number.

856639 is a deficient number, since it is larger than the sum of its proper divisors (141281).

856639 is a wasteful number, since it uses less digits than its factorization.

856639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2369.

The product of its digits is 38880, while the sum is 37.

The square root of 856639 is about 925.5479458137. The cubic root of 856639 is about 94.9728084690.

It can be divided in two parts, 85 and 6639, that added together give a square (6724 = 82²).

The spelling of 856639 in words is "eight hundred fifty-six thousand, six hundred thirty-nine".