2561000258661 has 16 divisors (see below), whose sum is σ = 3696000384384. Its totient is φ = 1568000153664.

The previous prime is 2561000258611. The next prime is 2561000258689. The reversal of 2561000258661 is 1668520001652.

It is not a de Polignac number, because 2561000258661 - 2¹⁸ = 2560999996517 is a prime.

2561000258661 is a modest number, since divided by 258661 gives 25610 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2561000258611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 166659001 + ... + 166674366.

It is an arithmetic number, because the mean of its divisors is an integer number (231000024024).

Almost surely, 2^{2561000258661} is an apocalyptic number.

It is an amenable number.

2561000258661 is a deficient number, since it is larger than the sum of its proper divisors (1135000125723).

2561000258661 is a wasteful number, since it uses less digits than its factorization.

2561000258661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 333333580.

The product of its (nonzero) digits is 172800, while the sum is 42.

The spelling of 2561000258661 in words is "two trillion, five hundred sixty-one billion, two hundred fifty-eight thousand, six hundred sixty-one".