11891 has 8 divisors (see below), whose sum is σ = 13824. Its totient is φ = 10120.

The previous prime is 11887. The next prime is 11897. The reversal of 11891 is 19811.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 11891 - 2² = 11887 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (11897) 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, 230 + ... + 276.

It is an arithmetic number, because the mean of its divisors is an integer number (1728).

2¹¹⁸⁹¹ is an apocalyptic number.

11891 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

11891 is a deficient number, since it is larger than the sum of its proper divisors (1933).

11891 is a wasteful number, since it uses less digits than its factorization.

11891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81.

The product of its digits is 72, while the sum is 20.

The square root of 11891 is about 109.0458619114. The cubic root of 11891 is about 22.8247550966.

Adding to 11891 its sum of digits (20), we get a palindrome (11911).

It can be divided in two parts, 11 and 891, that multiplied together give a square (9801 = 99²).

The spelling of 11891 in words is "eleven thousand, eight hundred ninety-one".