2991 has 4 divisors (see below), whose sum is σ = 3992. Its totient is φ = 1992.

The previous prime is 2971. The next prime is 2999. The reversal of 2991 is 1992.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 2991 - 2⁶ = 2927 is a prime.

It is a D-number.

It is a Duffinian number.

It is a plaindrome in base 11 and base 14.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2999) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 496 + ... + 501.

It is an arithmetic number, because the mean of its divisors is an integer number (998).

2991 is a deficient number, since it is larger than the sum of its proper divisors (1001).

2991 is an equidigital number, since it uses as much as digits as its factorization.

2991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1000.

The product of its digits is 162, while the sum is 21.

The square root of 2991 is about 54.6900356555. The cubic root of 2991 is about 14.4080587608.

Subtracting from 2991 its reverse (1992), we obtain a palindrome (999).

It can be divided in two parts, 299 and 1, that added together give a triangular number (300 = T₂₄).

The spelling of 2991 in words is "two thousand, nine hundred ninety-one".