2561000221655 has 16 divisors (see below), whose sum is σ = 3082681588320. Its totient is φ = 2042482219008.

The previous prime is 2561000221639. The next prime is 2561000221657. The reversal of 2561000221655 is 5561220001652.

It is a cyclic number.

It is not a de Polignac number, because 2561000221655 - 2⁴ = 2561000221639 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2561000221657) 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, 6913019 + ... + 7274051.

It is an arithmetic number, because the mean of its divisors is an integer number (192667599270).

Almost surely, 2^{2561000221655} is an apocalyptic number.

2561000221655 is a deficient number, since it is larger than the sum of its proper divisors (521681366665).

2561000221655 is a wasteful number, since it uses less digits than its factorization.

2561000221655 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 365410.

The product of its (nonzero) digits is 36000, while the sum is 35.

The spelling of 2561000221655 in words is "two trillion, five hundred sixty-one billion, two hundred twenty-one thousand, six hundred fifty-five".