256205721601 has 4 divisors (see below), whose sum is σ = 256206749652. Its totient is φ = 256204693552.

The previous prime is 256205721571. The next prime is 256205721659. The reversal of 256205721601 is 106127502652.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 40552293376 + 215653428225 = 201376^2 + 464385^2 .

It is a cyclic number.

It is not a de Polignac number, because 256205721601 - 2⁹ = 256205721089 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (256209721601) 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, 122715 + ... + 726271.

It is an arithmetic number, because the mean of its divisors is an integer number (64051687413).

Almost surely, 2^256205721601 is an apocalyptic number.

It is an amenable number.

256205721601 is a deficient number, since it is larger than the sum of its proper divisors (1028051).

256205721601 is an equidigital number, since it uses as much as digits as its factorization.

256205721601 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1028050.

The product of its (nonzero) digits is 50400, while the sum is 37.

The spelling of 256205721601 in words is "two hundred fifty-six billion, two hundred five million, seven hundred twenty-one thousand, six hundred one".