256691 has 4 divisors (see below), whose sum is σ = 258192. Its totient is φ = 255192.

The previous prime is 256687. The next prime is 256699. The reversal of 256691 is 196652.

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

It is a cyclic number.

It is not a de Polignac number, because 256691 - 2² = 256687 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256699) 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, 455 + ... + 848.

It is an arithmetic number, because the mean of its divisors is an integer number (64548).

2²⁵⁶⁶⁹¹ is an apocalyptic number.

256691 is a deficient number, since it is larger than the sum of its proper divisors (1501).

256691 is a wasteful number, since it uses less digits than its factorization.

256691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1500.

The product of its digits is 3240, while the sum is 29.

The square root of 256691 is about 506.6468197867. The cubic root of 256691 is about 63.5531206561.

The spelling of 256691 in words is "two hundred fifty-six thousand, six hundred ninety-one".