91998720 has 320 divisors, whose sum is σ = 359441280. Its totient is φ = 22302720.

The previous prime is 91998691. The next prime is 91998727. The reversal of 91998720 is 2789919.

It is a tau number, because it is divible by the number of its divisors (320).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91998727) 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, 8363515 + ... + 8363525.

It is an arithmetic number, because the mean of its divisors is an integer number (1123254).

Almost surely, 2^91998720 is an apocalyptic number.

91998720 is a gapful number since it is divisible by the number (90) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 91998720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (179720640).

91998720 is an abundant number, since it is smaller than the sum of its proper divisors (267442560).

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

91998720 is an equidigital number, since it uses as much as digits as its factorization.

91998720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 65 (or 21 counting only the distinct ones).

The product of its (nonzero) digits is 81648, while the sum is 45.

The square root of 91998720 is about 9591.5963217809. The cubic root of 91998720 is about 451.4336499226.

The spelling of 91998720 in words is "ninety-one million, nine hundred ninety-eight thousand, seven hundred twenty".