256431640 has 32 divisors (see below), whose sum is σ = 579292560. Its totient is φ = 102160000.

The previous prime is 256431631. The next prime is 256431647. The reversal of 256431640 is 46134652.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256431647) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 2731 + ... + 22810.

Almost surely, 2^256431640 is an apocalyptic number.

256431640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

256431640 is an abundant number, since it is smaller than the sum of its proper divisors (322860920).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

256431640 is a wasteful number, since it uses less digits than its factorization.

256431640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25803 (or 25799 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 31.

The square root of 256431640 is about 16013.4830689641. The cubic root of 256431640 is about 635.3170880032.

The spelling of 256431640 in words is "two hundred fifty-six million, four hundred thirty-one thousand, six hundred forty".