256205691 has 96 divisors (see below), whose sum is σ = 473765760. Its totient is φ = 130056192.

The previous prime is 256205689. The next prime is 256205713. The reversal of 256205691 is 196502652.

256205691 is a `hidden beast` number, since 2 + 562 + 0 + 5 + 6 + 91 = 666.

It is not a de Polignac number, because 256205691 - 2¹ = 256205689 is a prime.

It is a super-2 number, since 2×256205691² = 131282712201574962, which contains 22 as substring.

256205691 is a modest number, since divided by 5691 gives 2562 as remainder.

It is not an unprimeable number, because it can be changed into a prime (256205491) by changing a digit.

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 95 ways as a sum of consecutive naturals, for example, 2267251 + ... + 2267363.

It is an arithmetic number, because the mean of its divisors is an integer number (4935060).

Almost surely, 2^256205691 is an apocalyptic number.

256205691 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

256205691 is a deficient number, since it is larger than the sum of its proper divisors (217560069).

256205691 is a wasteful number, since it uses less digits than its factorization.

256205691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 245 (or 242 counting only the distinct ones).

The product of its (nonzero) digits is 32400, while the sum is 36.

The square root of 256205691 is about 16006.4265531067. The cubic root of 256205691 is about 635.1304346933.

The spelling of 256205691 in words is "two hundred fifty-six million, two hundred five thousand, six hundred ninety-one".