18961 has 4 divisors (see below), whose sum is σ = 19312. Its totient is φ = 18612.

The previous prime is 18959. The next prime is 18973. The reversal of 18961 is 16981.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 18961 - 2¹ = 18959 is a prime.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 75 + ... + 208.

It is an arithmetic number, because the mean of its divisors is an integer number (4828).

2¹⁸⁹⁶¹ is an apocalyptic number.

18961 is the 80-th hex number.

It is an amenable number.

18961 is a deficient number, since it is larger than the sum of its proper divisors (351).

18961 is an equidigital number, since it uses as much as digits as its factorization.

18961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 350.

The product of its digits is 432, while the sum is 25.

The square root of 18961 is about 137.6989469822. The cubic root of 18961 is about 26.6657464960.

It can be divided in two parts, 18 and 961, that added together give a palindrome (979).

The spelling of 18961 in words is "eighteen thousand, nine hundred sixty-one".