8991661998 has 64 divisors (see below), whose sum is σ = 21675382272. Its totient is φ = 2452961280.

The previous prime is 8991661993. The next prime is 8991662039.

8991661998 is nontrivially palindromic in base 10.

It is a Harshad number since it is a multiple of its sum of digits (66).

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 polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 148411 + ... + 200022.

It is an arithmetic number, because the mean of its divisors is an integer number (338677848).

Almost surely, 2^8991661998 is an apocalyptic number.

8991661998 is an abundant number, since it is smaller than the sum of its proper divisors (12683720274).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

8991661998 is a wasteful number, since it uses less digits than its factorization.

8991661998 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 348489.

The product of its digits is 15116544, while the sum is 66.

The square root of 8991661998 is about 94824.3744930595. The cubic root of 8991661998 is about 2079.4412637245.

The spelling of 8991661998 in words is "eight billion, nine hundred ninety-one million, six hundred sixty-one thousand, nine hundred ninety-eight".