256421591 has 4 divisors (see below), whose sum is σ = 271505232. Its totient is φ = 241337952.

The previous prime is 256421573. The next prime is 256421609. The reversal of 256421591 is 195124652.

It is a happy number.

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

It is an interprime number because it is at equal distance from previous prime (256421573) and next prime (256421609).

It is a cyclic number.

It is not a de Polignac number, because 256421591 - 2¹⁴ = 256405207 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256471591) 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 3 ways as a sum of consecutive naturals, for example, 7541795 + ... + 7541828.

It is an arithmetic number, because the mean of its divisors is an integer number (67876308).

Almost surely, 2^256421591 is an apocalyptic number.

256421591 is a deficient number, since it is larger than the sum of its proper divisors (15083641).

256421591 is a wasteful number, since it uses less digits than its factorization.

256421591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15083640.

The product of its digits is 21600, while the sum is 35.

The square root of 256421591 is about 16013.1692990488. The cubic root of 256421591 is about 635.3087889950.

The spelling of 256421591 in words is "two hundred fifty-six million, four hundred twenty-one thousand, five hundred ninety-one".