2561561627891 has 16 divisors (see below), whose sum is σ = 2942502038784. Its totient is φ = 2184373058784.

The previous prime is 2561561627813. The next prime is 2561561627897. The reversal of 2561561627891 is 1987261651652.

2561561627891 is digitally balanced in base 2 and base 3, because in such bases it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 2561561627891 - 2¹⁸ = 2561561365747 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 2561561627891.

It is not an unprimeable number, because it can be changed into a prime (2561561627897) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 44103116 + ... + 44161158.

It is an arithmetic number, because the mean of its divisors is an integer number (183906377424).

Almost surely, 2^{2561561627891} is an apocalyptic number.

2561561627891 is a deficient number, since it is larger than the sum of its proper divisors (380940410893).

2561561627891 is a wasteful number, since it uses less digits than its factorization.

2561561627891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90250.

The product of its digits is 10886400, while the sum is 59.

The spelling of 2561561627891 in words is "two trillion, five hundred sixty-one billion, five hundred sixty-one million, six hundred twenty-seven thousand, eight hundred ninety-one".