256507665 has 8 divisors (see below), whose sum is σ = 410412288. Its totient is φ = 136804080.

The previous prime is 256507649. The next prime is 256507687. The reversal of 256507665 is 566705652.

It is a happy number.

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

It is not a de Polignac number, because 256507665 - 2⁴ = 256507649 is a prime.

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8550241 + ... + 8550270.

It is an arithmetic number, because the mean of its divisors is an integer number (51301536).

Almost surely, 2^256507665 is an apocalyptic number.

It is an amenable number.

256507665 is a deficient number, since it is larger than the sum of its proper divisors (153904623).

256507665 is a wasteful number, since it uses less digits than its factorization.

256507665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17100519.

The product of its (nonzero) digits is 378000, while the sum is 42.

The square root of 256507665 is about 16015.8566739341. The cubic root of 256507665 is about 635.3798665397.

The spelling of 256507665 in words is "two hundred fifty-six million, five hundred seven thousand, six hundred sixty-five".