17861 has 4 divisors (see below), whose sum is σ = 18252. Its totient is φ = 17472.

The previous prime is 17851. The next prime is 17863. The reversal of 17861 is 16871.

17861 = 94² + 95².

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 + 9025 = 94^2 + 95^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-17861 is a prime.

It is a Duffinian number.

It is a plaindrome in base 11.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (17863) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 116 + ... + 221.

It is an arithmetic number, because the mean of its divisors is an integer number (4563).

17861 is the 95-th centered square number.

It is an amenable number.

17861 is a deficient number, since it is larger than the sum of its proper divisors (391).

17861 is an equidigital number, since it uses as much as digits as its factorization.

17861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 390.

The product of its digits is 336, while the sum is 23.

The square root of 17861 is about 133.6450522840. The cubic root of 17861 is about 26.1397797219.

Subtracting from 17861 its reverse (16871), we obtain a triangular number (990 = T₄₄).

It can be divided in two parts, 17 and 861, that added together give a palindrome (878).

The spelling of 17861 in words is "seventeen thousand, eight hundred sixty-one".