91989900 has 108 divisors (see below), whose sum is σ = 295166872. Its totient is φ = 23950080.

The previous prime is 91989899. The next prime is 91989901. The reversal of 91989900 is 998919.

It is an interprime number because it is at equal distance from previous prime (91989899) and next prime (91989901).

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

It is not an unprimeable number, because it can be changed into a prime (91989901) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 37512 + ... + 39888.

Almost surely, 2^91989900 is an apocalyptic number.

91989900 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 91989900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (147583436).

91989900 is an abundant number, since it is smaller than the sum of its proper divisors (203176972).

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

91989900 is a wasteful number, since it uses less digits than its factorization.

91989900 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2440 (or 2430 counting only the distinct ones).

The product of its (nonzero) digits is 52488, while the sum is 45.

The square root of 91989900 is about 9591.1365332790. The cubic root of 91989900 is about 451.4192230116.

The spelling of 91989900 in words is "ninety-one million, nine hundred eighty-nine thousand, nine hundred".