2561971568641 has 4 divisors (see below), whose sum is σ = 2563021129284. Its totient is φ = 2560922008000.

The previous prime is 2561971568621. The next prime is 2561971568647. The reversal of 2561971568641 is 1468651791652.

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 1368806401600 + 1193165167041 = 1169960^2 + 1092321^2 .

It is a cyclic number.

It is not a de Polignac number, because 2561971568641 - 2⁵ = 2561971568609 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 2561971568641.

It is not an unprimeable number, because it can be changed into a prime (2561971568647) 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, 524776660 + ... + 524781541.

It is an arithmetic number, because the mean of its divisors is an integer number (640755282321).

Almost surely, 2^{2561971568641} is an apocalyptic number.

It is an amenable number.

2561971568641 is a deficient number, since it is larger than the sum of its proper divisors (1049560643).

2561971568641 is a wasteful number, since it uses less digits than its factorization.

2561971568641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1049560642.

The product of its digits is 21772800, while the sum is 61.

The spelling of 2561971568641 in words is "two trillion, five hundred sixty-one billion, nine hundred seventy-one million, five hundred sixty-eight thousand, six hundred forty-one".