256815720 has 192 divisors, whose sum is σ = 960261120. Its totient is φ = 58309632.

The previous prime is 256815703. The next prime is 256815751. The reversal of 256815720 is 27518652.

It is a happy number.

256815720 is a `hidden beast` number, since 2 + 5 + 6 + 81 + 572 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 561732 + ... + 562188.

It is an arithmetic number, because the mean of its divisors is an integer number (5001360).

Almost surely, 2^256815720 is an apocalyptic number.

256815720 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 256815720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (480130560).

256815720 is an abundant number, since it is smaller than the sum of its proper divisors (703445400).

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

256815720 is a wasteful number, since it uses less digits than its factorization.

256815720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 704 (or 697 counting only the distinct ones).

The product of its (nonzero) digits is 33600, while the sum is 36.

The square root of 256815720 is about 16025.4709759183. The cubic root of 256815720 is about 635.6341196848.

The spelling of 256815720 in words is "two hundred fifty-six million, eight hundred fifteen thousand, seven hundred twenty".