256440773581 has 4 divisors (see below), whose sum is σ = 256454228032. Its totient is φ = 256427319132.

The previous prime is 256440773549. The next prime is 256440773587. The reversal of 256440773581 is 185377044652.

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 256440773581 - 2⁵ = 256440773549 is a prime.

It is a super-2 number, since 2×256440773581² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256440773587) 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, 6698595 + ... + 6736768.

It is an arithmetic number, because the mean of its divisors is an integer number (64113557008).

Almost surely, 2^256440773581 is an apocalyptic number.

It is an amenable number.

256440773581 is a deficient number, since it is larger than the sum of its proper divisors (13454451).

256440773581 is a wasteful number, since it uses less digits than its factorization.

256440773581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13454450.

The product of its (nonzero) digits is 5644800, while the sum is 52.

The spelling of 256440773581 in words is "two hundred fifty-six billion, four hundred forty million, seven hundred seventy-three thousand, five hundred eighty-one".