11861 has 4 divisors (see below), whose sum is σ = 12300. Its totient is φ = 11424.

The previous prime is 11839. The next prime is 11863. The reversal of 11861 is 16811.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 8836 + 3025 = 94^2 + 55^2 .

It is a cyclic number.

It is not a de Polignac number, because 11861 - 2¹⁰ = 10837 is a prime.

It is a Duffinian number.

It is a plaindrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11863) 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, 176 + ... + 233.

It is an arithmetic number, because the mean of its divisors is an integer number (3075).

2¹¹⁸⁶¹ is an apocalyptic number.

It is an amenable number.

11861 is a deficient number, since it is larger than the sum of its proper divisors (439).

11861 is an equidigital number, since it uses as much as digits as its factorization.

11861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 438.

The product of its digits is 48, while the sum is 17.

The square root of 11861 is about 108.9082182390. The cubic root of 11861 is about 22.8055439478.

Subtracting 11861 from its reverse (16811), we obtain a triangular number (4950 = T₉₉).

The spelling of 11861 in words is "eleven thousand, eight hundred sixty-one".