256781605 has 8 divisors (see below), whose sum is σ = 308286072. Its totient is φ = 205326528.

The previous prime is 256781597. The next prime is 256781621. The reversal of 256781605 is 506187652.

It can be written as a sum of positive squares in 4 ways, for example, as 61732449 + 195049156 = 7857^2 + 13966^2 .

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 256781605 - 2³ = 256781597 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 267 + ... + 22663.

It is an arithmetic number, because the mean of its divisors is an integer number (38535759).

Almost surely, 2^256781605 is an apocalyptic number.

It is an amenable number.

256781605 is a deficient number, since it is larger than the sum of its proper divisors (51504467).

256781605 is a wasteful number, since it uses less digits than its factorization.

256781605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24695.

The product of its (nonzero) digits is 100800, while the sum is 40.

The square root of 256781605 is about 16024.4065412732. The cubic root of 256781605 is about 635.6059728898.

The spelling of 256781605 in words is "two hundred fifty-six million, seven hundred eighty-one thousand, six hundred five".