256577375721 has 4 divisors (see below), whose sum is σ = 342103167632. Its totient is φ = 171051583812.

The previous prime is 256577375713. The next prime is 256577375759. The reversal of 256577375721 is 127573775652.

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 not a de Polignac number, because 256577375721 - 2³ = 256577375713 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (256577375321) 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, 42762895951 + ... + 42762895956.

It is an arithmetic number, because the mean of its divisors is an integer number (85525791908).

Almost surely, 2^256577375721 is an apocalyptic number.

It is an amenable number.

256577375721 is a deficient number, since it is larger than the sum of its proper divisors (85525791911).

256577375721 is an equidigital number, since it uses as much as digits as its factorization.

256577375721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85525791910.

The product of its digits is 21609000, while the sum is 57.

The spelling of 256577375721 in words is "two hundred fifty-six billion, five hundred seventy-seven million, three hundred seventy-five thousand, seven hundred twenty-one".