256691540 has 48 divisors (see below), whose sum is σ = 623884800. Its totient is φ = 86890752.

The previous prime is 256691507. The next prime is 256691543. The reversal of 256691540 is 45196652.

It is a junction number, because it is equal to n+sod(n) for n = 256691494 and 256691503.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256691543) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 545 + ... + 22664.

It is an arithmetic number, because the mean of its divisors is an integer number (12997600).

Almost surely, 2^256691540 is an apocalyptic number.

256691540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 256691540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (311942400).

256691540 is an abundant number, since it is smaller than the sum of its proper divisors (367193260).

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

256691540 is a wasteful number, since it uses less digits than its factorization.

256691540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23304 (or 23302 counting only the distinct ones).

The product of its (nonzero) digits is 64800, while the sum is 38.

The square root of 256691540 is about 16021.5960503316. The cubic root of 256691540 is about 635.5316522154.

The spelling of 256691540 in words is "two hundred fifty-six million, six hundred ninety-one thousand, five hundred forty".