256561165 has 16 divisors (see below), whose sum is σ = 353808000. Its totient is φ = 174951360.

The previous prime is 256561147. The next prime is 256561183. The reversal of 256561165 is 561165652.

It is an interprime number because it is at equal distance from previous prime (256561147) and next prime (256561183).

It is not a de Polignac number, because 256561165 - 2¹⁹ = 256036877 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13915 + ... + 26584.

It is an arithmetic number, because the mean of its divisors is an integer number (22113000).

Almost surely, 2^256561165 is an apocalyptic number.

It is an amenable number.

256561165 is a deficient number, since it is larger than the sum of its proper divisors (97246835).

256561165 is a wasteful number, since it uses less digits than its factorization.

256561165 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40692.

The product of its digits is 54000, while the sum is 37.

The square root of 256561165 is about 16017.5268065953. The cubic root of 256561165 is about 635.4240373572.

The spelling of 256561165 in words is "two hundred fifty-six million, five hundred sixty-one thousand, one hundred sixty-five".