256640400 has 225 divisors, whose sum is σ = 931527091. Its totient is φ = 67668480.

The previous prime is 256640389. The next prime is 256640407. The reversal of 256640400 is 4046652.

It is a happy number.

The square root of 256640400 is 16020.

It is a perfect power (a square), and thus also a powerful number.

256640400 is a `hidden beast` number, since 256 + 6 + 4 + 0 + 400 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 53406864 + 203233536 = 7308^2 + 14256^2 .

It is a tau number, because it is divible by the number of its divisors (225).

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (256640407) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 2883556 + ... + 2883644.

Almost surely, 2^256640400 is an apocalyptic number.

256640400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

256640400 is the 16020-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 256640400

256640400 is an abundant number, since it is smaller than the sum of its proper divisors (674886691).

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

256640400 is an equidigital number, since it uses as much as digits as its factorization.

256640400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 208 (or 99 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 27.

The cubic root of 256640400 is about 635.4894442963.

The spelling of 256640400 in words is "two hundred fifty-six million, six hundred forty thousand, four hundred".