8561011981 has 2 divisors, whose sum is σ = 8561011982. Its totient is φ = 8561011980.

The previous prime is 8561011969. The next prime is 8561012059. The reversal of 8561011981 is 1891101658.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 5684406025 + 2876605956 = 75395^2 + 53634^2 .

It is a cyclic number.

It is not a de Polignac number, because 8561011981 - 2¹⁵ = 8560979213 is a prime.

It is a super-3 number, since 3×8561011981³ (a number of 31 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (8561011951) 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 as a sum of consecutive naturals, namely, 4280505990 + 4280505991.

It is an arithmetic number, because the mean of its divisors is an integer number (4280505991).

Almost surely, 2^8561011981 is an apocalyptic number.

It is an amenable number.

8561011981 is a deficient number, since it is larger than the sum of its proper divisors (1).

8561011981 is an equidigital number, since it uses as much as digits as its factorization.

8561011981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 17280, while the sum is 40.

The square root of 8561011981 is about 92525.7368573739. The cubic root of 8561011981 is about 2045.6988527770.

The spelling of 8561011981 in words is "eight billion, five hundred sixty-one million, eleven thousand, nine hundred eighty-one".