8991001998 has 128 divisors (see below), whose sum is σ = 22474160640. Its totient is φ = 2640418560.

The previous prime is 8991001997. The next prime is 8991002011.

8991001998 is nontrivially palindromic in base 10.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8991001997) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 6878461 + ... + 6879767.

It is an arithmetic number, because the mean of its divisors is an integer number (175579380).

Almost surely, 2^8991001998 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 8991001998, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (11237080320).

8991001998 is an abundant number, since it is smaller than the sum of its proper divisors (13483158642).

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

8991001998 is a wasteful number, since it uses less digits than its factorization.

8991001998 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1679 (or 1673 counting only the distinct ones).

The product of its (nonzero) digits is 419904, while the sum is 54.

The square root of 8991001998 is about 94820.8943113278. The cubic root of 8991001998 is about 2079.3903845575.

The spelling of 8991001998 in words is "eight billion, nine hundred ninety-one million, one thousand, nine hundred ninety-eight".