256778809 has 4 divisors (see below), whose sum is σ = 293461504. Its totient is φ = 220096116.

The previous prime is 256778807. The next prime is 256778833. The reversal of 256778809 is 908877652.

256778809 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 256778809 - 2¹ = 256778807 is a prime.

It is not an unprimeable number, because it can be changed into a prime (256778803) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18341337 + ... + 18341350.

It is an arithmetic number, because the mean of its divisors is an integer number (73365376).

Almost surely, 2^256778809 is an apocalyptic number.

It is an amenable number.

256778809 is a deficient number, since it is larger than the sum of its proper divisors (36682695).

256778809 is an equidigital number, since it uses as much as digits as its factorization.

256778809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36682694.

The product of its (nonzero) digits is 1693440, while the sum is 52.

The square root of 256778809 is about 16024.3192991153. The cubic root of 256778809 is about 635.6036659219.

The spelling of 256778809 in words is "two hundred fifty-six million, seven hundred seventy-eight thousand, eight hundred nine".