856921 has 8 divisors (see below), whose sum is σ = 955080. Its totient is φ = 763392.

The previous prime is 856909. The next prime is 856927. The reversal of 856921 is 129658.

856921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 151321 + 705600 = 389^2 + 840^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-856921 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (856927) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 760 + ... + 1513.

It is an arithmetic number, because the mean of its divisors is an integer number (119385).

2⁸⁵⁶⁹²¹ is an apocalyptic number.

It is an amenable number.

856921 is a deficient number, since it is larger than the sum of its proper divisors (98159).

856921 is a wasteful number, since it uses less digits than its factorization.

856921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2315.

The product of its digits is 4320, while the sum is 31.

The square root of 856921 is about 925.7002754672. The cubic root of 856921 is about 94.9832288030.

The spelling of 856921 in words is "eight hundred fifty-six thousand, nine hundred twenty-one".