99891 has 12 divisors (see below), whose sum is σ = 157560. Its totient is φ = 60480.

The previous prime is 99881. The next prime is 99901. The reversal of 99891 is 19899.

It is an interprime number because it is at equal distance from previous prime (99881) and next prime (99901).

It is not a de Polignac number, because 99891 - 2⁵ = 99859 is a prime.

99891 is a modest number, since divided by 891 gives 99 as remainder.

It is a zygodrome in base 2.

It is not an unprimeable number, because it can be changed into a prime (99871) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 406 + ... + 603.

It is an arithmetic number, because the mean of its divisors is an integer number (13130).

2⁹⁹⁸⁹¹ is an apocalyptic number.

99891 is a deficient number, since it is larger than the sum of its proper divisors (57669).

99891 is a wasteful number, since it uses less digits than its factorization.

99891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1026 (or 1023 counting only the distinct ones).

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

The square root of 99891 is about 316.0553748950. The cubic root of 99891 is about 46.3990177656.

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

The spelling of 99891 in words is "ninety-nine thousand, eight hundred ninety-one".