16665 has 16 divisors (see below), whose sum is σ = 29376. Its totient is φ = 8000.

The previous prime is 16661. The next prime is 16673. The reversal of 16665 is 56661.

It is not a de Polignac number, because 16665 - 2² = 16661 is a prime.

Its product of digits (1080) is a multiple of the sum of its prime divisors (120).

It is a Curzon number.

16665 is a lucky number.

It is a plaindrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (16661) 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 15 ways as a sum of consecutive naturals, for example, 115 + ... + 215.

It is an arithmetic number, because the mean of its divisors is an integer number (1836).

2¹⁶⁶⁶⁵ is an apocalyptic number.

16665 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

16665 is a deficient number, since it is larger than the sum of its proper divisors (12711).

16665 is a wasteful number, since it uses less digits than its factorization.

16665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 120.

The product of its digits is 1080, while the sum is 24.

The square root of 16665 is about 129.0929897400. The cubic root of 16665 is about 25.5427962631.

Subtracting from 16665 its sum of digits (24), we obtain a square (16641 = 129²).

It can be divided in two parts, 166 and 65, that added together give a triangular number (231 = T₂₁).

The spelling of 16665 in words is "sixteen thousand, six hundred sixty-five".