256436640 has 144 divisors (see below), whose sum is σ = 898927848. Its totient is φ = 66521088.

The previous prime is 256436639. The next prime is 256436651. The reversal of 256436640 is 46634652.

256436640 is a `hidden beast` number, since 2 + 5 + 6 + 4 + 3 + 6 + 640 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 253573776 + 2862864 = 15924^2 + 1692^2 .

It is a tau number, because it is divible by the number of its divisors (144).

It is a hoax number, since the sum of its digits (36) 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 (36).

It is a junction number, because it is equal to n+sod(n) for n = 256436595 and 256436604.

It is a congruent number.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 50874 + ... + 55686.

Almost surely, 2^256436640 is an apocalyptic number.

256436640 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 256436640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (449463924).

256436640 is an abundant number, since it is smaller than the sum of its proper divisors (642491208).

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

256436640 is a wasteful number, since it uses less digits than its factorization.

256436640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4871 (or 4860 counting only the distinct ones).

The product of its (nonzero) digits is 103680, while the sum is 36.

The square root of 256436640 is about 16013.6391866434. The cubic root of 256436640 is about 635.3212171931.

It can be divided in two parts, 2564 and 36640, that added together give a square (39204 = 198²).

The spelling of 256436640 in words is "two hundred fifty-six million, four hundred thirty-six thousand, six hundred forty".