2191 has 4 divisors (see below), whose sum is σ = 2512.
Its totient is φ = 1872.
The previous prime is 2179. The next prime is 2203. The reversal of 2191 is 1912.
Adding to 2191 its product of digits (18), we get a square (2209 = 472).
2191 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.
It is a semiprime because it is the product of two primes.
It is an interprime number because it is at equal distance from previous prime (2179) and next prime (2203).
It is a cyclic number.
It is not a de Polignac number, because 2191 - 27 = 2063 is a prime.
It is a Duffinian number.
It is a plaindrome in base 16.
It is a nialpdrome in base 13.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (2111) 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, 150 + ... + 163.
It is an arithmetic number, because the mean of its divisors is an integer number (628).
2191 is a deficient number, since it is larger than the sum of its proper divisors (321).
2191 is an equidigital number, since it uses as much as digits as its factorization.
2191 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 320.
The product of its digits is 18, while the sum is 13.
The square root of 2191 is about 46.8081189539.
The cubic root of 2191 is about 12.9881548909.
The spelling of 2191 in words is "two thousand, one hundred ninety-one".