91099890 has 80 divisors (see below), whose sum is σ = 279968832. Its totient is φ = 20821536.

The previous prime is 91099873. The next prime is 91099891. The reversal of 91099890 is 9899019.

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 (91099891) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 2364 + ... + 13703.

Almost surely, 2^91099890 is an apocalyptic number.

91099890 is a gapful number since it is divisible by the number (90) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 91099890, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (139984416).

91099890 is an abundant number, since it is smaller than the sum of its proper divisors (188868942).

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

91099890 is a wasteful number, since it uses less digits than its factorization.

91099890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16093 (or 16084 counting only the distinct ones).

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

The square root of 91099890 is about 9544.6262367890. The cubic root of 91099890 is about 449.9586628695.

The spelling of 91099890 in words is "ninety-one million, ninety-nine thousand, eight hundred ninety".