216645 has 32 divisors (see below), whose sum is σ = 411264. Its totient is φ = 96000.

The previous prime is 216641. The next prime is 216647. The reversal of 216645 is 546612.

216645 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 216645 - 2² = 216641 is a prime.

It is a Curzon number.

216645 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216641) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2095 + ... + 2195.

It is an arithmetic number, because the mean of its divisors is an integer number (12852).

2²¹⁶⁶⁴⁵ is an apocalyptic number.

It is an amenable number.

216645 is a deficient number, since it is larger than the sum of its proper divisors (194619).

216645 is a wasteful number, since it uses less digits than its factorization.

216645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133.

The product of its digits is 1440, while the sum is 24.

The square root of 216645 is about 465.4513938104. The cubic root of 216645 is about 60.0596628749.

It can be divided in two parts, 2166 and 45, that added together give a triangular number (2211 = T₆₆).

The spelling of 216645 in words is "two hundred sixteen thousand, six hundred forty-five".