8561011991 has 8 divisors (see below), whose sum is σ = 9787668384. Its totient is φ = 7335269280.

The previous prime is 8561011981. The next prime is 8561012059. The reversal of 8561011991 is 1991101658.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-8561011991 is a prime.

It is a super-3 number, since 3×8561011991³ (a number of 31 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8561011951) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 208220 + ... + 245921.

It is an arithmetic number, because the mean of its divisors is an integer number (1223458548).

Almost surely, 2^8561011991 is an apocalyptic number.

8561011991 is a deficient number, since it is larger than the sum of its proper divisors (1226656393).

8561011991 is a wasteful number, since it uses less digits than its factorization.

8561011991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 456841.

The product of its (nonzero) digits is 19440, while the sum is 41.

The square root of 8561011991 is about 92525.7369114129. The cubic root of 8561011991 is about 2045.6988535735.

The spelling of 8561011991 in words is "eight billion, five hundred sixty-one million, eleven thousand, nine hundred ninety-one".