256421391 has 4 divisors (see below), whose sum is σ = 341895192. Its totient is φ = 170947592.

The previous prime is 256421383. The next prime is 256421437. The reversal of 256421391 is 193124652.

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

It is a cyclic number.

It is not a de Polignac number, because 256421391 - 2³ = 256421383 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256421351) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 42736896 + ... + 42736901.

It is an arithmetic number, because the mean of its divisors is an integer number (85473798).

Almost surely, 2^256421391 is an apocalyptic number.

256421391 is a deficient number, since it is larger than the sum of its proper divisors (85473801).

256421391 is an equidigital number, since it uses as much as digits as its factorization.

256421391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 85473800.

The product of its digits is 12960, while the sum is 33.

The square root of 256421391 is about 16013.1630541876. The cubic root of 256421391 is about 635.3086238220.

The spelling of 256421391 in words is "two hundred fifty-six million, four hundred twenty-one thousand, three hundred ninety-one".