93991 has 4 divisors (see below), whose sum is σ = 94672. Its totient is φ = 93312.

The previous prime is 93983. The next prime is 93997. The reversal of 93991 is 19939.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 19939 = 127 ⋅157.

It is a 7-Lehmer number, since φ(93991) divides (93991-1)⁷.

It is a cyclic number.

It is not a de Polignac number, because 93991 - 2³ = 93983 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (93997) 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 3 ways as a sum of consecutive naturals, for example, 51 + ... + 436.

It is an arithmetic number, because the mean of its divisors is an integer number (23668).

2⁹³⁹⁹¹ is an apocalyptic number.

93991 is a deficient number, since it is larger than the sum of its proper divisors (681).

93991 is a wasteful number, since it uses less digits than its factorization.

93991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 680.

The product of its digits is 2187, while the sum is 31.

The square root of 93991 is about 306.5795166021. The cubic root of 93991 is about 45.4669082736.

The spelling of 93991 in words is "ninety-three thousand, nine hundred ninety-one".