19911 has 4 divisors (see below), whose sum is σ = 26552. Its totient is φ = 13272.

The previous prime is 19891. The next prime is 19913. The reversal of 19911 is 11991.

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

It is not a de Polignac number, because 19911 - 2¹¹ = 17863 is a prime.

It is a D-number.

It is a Duffinian number.

It is a nialpdrome in base 12.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19913) 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, 3316 + ... + 3321.

It is an arithmetic number, because the mean of its divisors is an integer number (6638).

2¹⁹⁹¹¹ is an apocalyptic number.

19911 is a deficient number, since it is larger than the sum of its proper divisors (6641).

19911 is an equidigital number, since it uses as much as digits as its factorization.

19911 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6640.

The product of its digits is 81, while the sum is 21.

The square root of 19911 is about 141.1063428766. The cubic root of 19911 is about 27.1038524318.

It can be divided in two parts, 199 and 11, that added together give a triangular number (210 = T₂₀).

The spelling of 19911 in words is "nineteen thousand, nine hundred eleven".