47991 has 8 divisors (see below), whose sum is σ = 67824. Its totient is φ = 30080.

The previous prime is 47981. The next prime is 48017. The reversal of 47991 is 19974.

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 47991 - 2¹¹ = 45943 is a prime.

It is a plaindrome in base 8 and base 14.

It is a nialpdrome in base 16.

It is a zygodrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (47911) 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, 420 + ... + 521.

It is an arithmetic number, because the mean of its divisors is an integer number (8478).

2⁴⁷⁹⁹¹ is an apocalyptic number.

47991 is a deficient number, since it is larger than the sum of its proper divisors (19833).

47991 is a wasteful number, since it uses less digits than its factorization.

47991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 961.

The product of its digits is 2268, while the sum is 30.

The square root of 47991 is about 219.0684824433. The cubic root of 47991 is about 36.3401403139.

Subtracting from 47991 its sum of digits (30), we obtain a square (47961 = 219²).

The spelling of 47991 in words is "forty-seven thousand, nine hundred ninety-one".