256891640 has 32 divisors (see below), whose sum is σ = 584977680. Its totient is φ = 101517312.

The previous prime is 256891631. The next prime is 256891643. The reversal of 256891640 is 46198652.

It is a happy number.

256891640 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256891643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 35369 + ... + 42008.

Almost surely, 2^256891640 is an apocalyptic number.

256891640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

256891640 is an abundant number, since it is smaller than the sum of its proper divisors (328086040).

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

256891640 is a wasteful number, since it uses less digits than its factorization.

256891640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 77471 (or 77467 counting only the distinct ones).

The product of its (nonzero) digits is 103680, while the sum is 41.

The square root of 256891640 is about 16027.8395300178. The cubic root of 256891640 is about 635.6967490128.

The spelling of 256891640 in words is "two hundred fifty-six million, eight hundred ninety-one thousand, six hundred forty".