91987 has 8 divisors (see below), whose sum is σ = 111456. Its totient is φ = 74112.

The previous prime is 91969. The next prime is 91997. The reversal of 91987 is 78919.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 91987 - 2¹¹ = 89939 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91957) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 268 + ... + 505.

It is an arithmetic number, because the mean of its divisors is an integer number (13932).

2⁹¹⁹⁸⁷ is an apocalyptic number.

91987 is a deficient number, since it is larger than the sum of its proper divisors (19469).

91987 is a wasteful number, since it uses less digits than its factorization.

91987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 797.

The product of its digits is 4536, while the sum is 34.

The square root of 91987 is about 303.2935871396. The cubic root of 91987 is about 45.1414479268.

The spelling of 91987 in words is "ninety-one thousand, nine hundred eighty-seven".