2011555561 has 2 divisors, whose sum is σ = 2011555562. Its totient is φ = 2011555560.

The previous prime is 2011555541. The next prime is 2011555603. The reversal of 2011555561 is 1655551102.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1329039936 + 682515625 = 36456^2 + 26125^2 .

It is a cyclic number.

It is not a de Polignac number, because 2011555561 - 2⁵ = 2011555529 is a prime.

It is not a weakly prime, because it can be changed into another prime (2011555541) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1005777780 + 1005777781.

It is an arithmetic number, because the mean of its divisors is an integer number (1005777781).

Almost surely, 2^2011555561 is an apocalyptic number.

It is an amenable number.

2011555561 is a deficient number, since it is larger than the sum of its proper divisors (1).

2011555561 is an equidigital number, since it uses as much as digits as its factorization.

2011555561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7500, while the sum is 31.

The square root of 2011555561 is about 44850.3685715067. The cubic root of 2011555561 is about 1262.3429073041.

The spelling of 2011555561 in words is "two billion, eleven million, five hundred fifty-five thousand, five hundred sixty-one".