16681 has 4 divisors (see below), whose sum is σ = 19072. Its totient is φ = 14292.

The previous prime is 16673. The next prime is 16691. The reversal of 16681 is 18661.

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 16681 - 2³ = 16673 is a prime.

It is a super-2 number, since 2×16681² = 556511522, which contains 22 as substring.

It is a Duffinian number.

It is a nialpdrome in base 7.

It is not an unprimeable number, because it can be changed into a prime (16631) 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, 1185 + ... + 1198.

It is an arithmetic number, because the mean of its divisors is an integer number (4768).

2¹⁶⁶⁸¹ is an apocalyptic number.

It is an amenable number.

16681 is a deficient number, since it is larger than the sum of its proper divisors (2391).

16681 is an equidigital number, since it uses as much as digits as its factorization.

16681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2390.

The product of its digits is 288, while the sum is 22.

The square root of 16681 is about 129.1549457048. The cubic root of 16681 is about 25.5509681607.

The spelling of 16681 in words is "sixteen thousand, six hundred eighty-one".