256635491 has 12 divisors (see below), whose sum is σ = 299851920. Its totient is φ = 219003120.

The previous prime is 256635469. The next prime is 256635493. The reversal of 256635491 is 194536652.

It is not a de Polignac number, because 256635491 - 2²² = 252441187 is a prime.

It is a super-2 number, since 2×256635491² = 131723550481622162, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (256635493) 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 11 ways as a sum of consecutive naturals, for example, 215 + ... + 22656.

It is an arithmetic number, because the mean of its divisors is an integer number (24987660).

Almost surely, 2^256635491 is an apocalyptic number.

256635491 is a deficient number, since it is larger than the sum of its proper divisors (43216429).

256635491 is a wasteful number, since it uses less digits than its factorization.

256635491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23114 (or 23107 counting only the distinct ones).

The product of its digits is 194400, while the sum is 41.

The square root of 256635491 is about 16019.8467845357. The cubic root of 256635491 is about 635.4853924043.

The spelling of 256635491 in words is "two hundred fifty-six million, six hundred thirty-five thousand, four hundred ninety-one".