89991 has 20 divisors (see below), whose sum is σ = 148104. Its totient is φ = 54000.

The previous prime is 89989. The next prime is 90001. The reversal of 89991 is 19998.

89991 = 3³ + 4³ + ... + 24³.

It is not a de Polignac number, because 89991 - 2¹ = 89989 is a prime.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (89491) 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 19 ways as a sum of consecutive naturals, for example, 841 + ... + 941.

2⁸⁹⁹⁹¹ is an apocalyptic number.

89991 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

89991 is a deficient number, since it is larger than the sum of its proper divisors (58113).

89991 is a wasteful number, since it uses less digits than its factorization.

89991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 124 (or 115 counting only the distinct ones).

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

The square root of 89991 is about 299.9849996250. The cubic root of 89991 is about 44.8125536142.

It can be divided in two parts, 899 and 91, that added together give a triangular number (990 = T₄₄).

The spelling of 89991 in words is "eighty-nine thousand, nine hundred ninety-one".