91998 has 24 divisors (see below), whose sum is σ = 210600. Its totient is φ = 28944.

The previous prime is 91997. The next prime is 92003. The reversal of 91998 is 89919.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 91998.

It is not an unprimeable number, because it can be changed into a prime (91997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 208 + ... + 476.

It is an arithmetic number, because the mean of its divisors is an integer number (8775).

2⁹¹⁹⁹⁸ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 91998, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (105300).

91998 is an abundant number, since it is smaller than the sum of its proper divisors (118602).

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

91998 is a wasteful number, since it uses less digits than its factorization.

91998 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 296 (or 293 counting only the distinct ones).

The product of its digits is 5832, while the sum is 36.

The square root of 91998 is about 303.3117208418. The cubic root of 91998 is about 45.1432472250.

It can be divided in two parts, 91 and 998, that added together give a square (1089 = 33²).

The spelling of 91998 in words is "ninety-one thousand, nine hundred ninety-eight".