16645 has 4 divisors (see below), whose sum is σ = 19980. Its totient is φ = 13312.

The previous prime is 16633. The next prime is 16649. The reversal of 16645 is 54661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 54661 = 47 ⋅1163.

It can be written as a sum of positive squares in 2 ways, for example, as 6241 + 10404 = 79^2 + 102^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16645 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a nialpdrome in base 12 and base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16649) 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, 1660 + ... + 1669.

It is an arithmetic number, because the mean of its divisors is an integer number (4995).

2¹⁶⁶⁴⁵ is an apocalyptic number.

It is an amenable number.

16645 is a deficient number, since it is larger than the sum of its proper divisors (3335).

16645 is an equidigital number, since it uses as much as digits as its factorization.

16645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3334.

The product of its digits is 720, while the sum is 22.

The square root of 16645 is about 129.0155029444. The cubic root of 16645 is about 25.5325740324.

The spelling of 16645 in words is "sixteen thousand, six hundred forty-five".