8991661999 has 8 divisors (see below), whose sum is σ = 9010883232. Its totient is φ = 8972461920.

The previous prime is 8991661993. The next prime is 8991662039. The reversal of 8991661999 is 9991661998.

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

It is a cyclic number.

It is not a de Polignac number, because 8991661999 - 2⁹ = 8991661487 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8991661993) 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 7 ways as a sum of consecutive naturals, for example, 1063302 + ... + 1071724.

It is an arithmetic number, because the mean of its divisors is an integer number (1126360404).

Almost surely, 2^8991661999 is an apocalyptic number.

8991661999 is a deficient number, since it is larger than the sum of its proper divisors (19221233).

8991661999 is a wasteful number, since it uses less digits than its factorization.

8991661999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10577.

The product of its digits is 17006112, while the sum is 67.

The square root of 8991661999 is about 94824.3744983324. The cubic root of 8991661999 is about 2079.4412638015.

Subtracting 8991661999 from its reverse (9991661998), we obtain a palindrome (999999999).

The spelling of 8991661999 in words is "eight billion, nine hundred ninety-one million, six hundred sixty-one thousand, nine hundred ninety-nine".