2155311061561 has 4 divisors (see below), whose sum is σ = 2463212641792. Its totient is φ = 1847409481332.

The previous prime is 2155311061549. The next prime is 2155311061597. The reversal of 2155311061561 is 1651601135512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 2155311061561 - 2¹¹ = 2155311059513 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 2155311061561.

It is not an unprimeable number, because it can be changed into a prime (2155311061361) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 153950790105 + ... + 153950790118.

It is an arithmetic number, because the mean of its divisors is an integer number (615803160448).

Almost surely, 2^{2155311061561} is an apocalyptic number.

It is an amenable number.

2155311061561 is a deficient number, since it is larger than the sum of its proper divisors (307901580231).

2155311061561 is an equidigital number, since it uses as much as digits as its factorization.

2155311061561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 307901580230.

The product of its (nonzero) digits is 27000, while the sum is 37.

The spelling of 2155311061561 in words is "two trillion, one hundred fifty-five billion, three hundred eleven million, sixty-one thousand, five hundred sixty-one".