256466665561 has 4 divisors (see below), whose sum is σ = 258187918500. Its totient is φ = 254745412624.

The previous prime is 256466665529. The next prime is 256466665579. The reversal of 256466665561 is 165566664652.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 37799136400 + 218667529161 = 194420^2 + 467619^2 .

It is a cyclic number.

It is not a de Polignac number, because 256466665561 - 2⁵ = 256466665529 is a prime.

It is a Smith number, since the sum of its digits (58) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 256466665496 and 256466665505.

It is not an unprimeable number, because it can be changed into a prime (256466665261) 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, 860626246 + ... + 860626543.

It is an arithmetic number, because the mean of its divisors is an integer number (64546979625).

Almost surely, 2^256466665561 is an apocalyptic number.

It is an amenable number.

256466665561 is a deficient number, since it is larger than the sum of its proper divisors (1721252939).

256466665561 is a wasteful number, since it uses less digits than its factorization.

256466665561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1721252938.

The product of its digits is 46656000, while the sum is 58.

Subtracting from 256466665561 its reverse (165566664652), we obtain a palindrome (90900000909).

The spelling of 256466665561 in words is "two hundred fifty-six billion, four hundred sixty-six million, six hundred sixty-five thousand, five hundred sixty-one".