216305 has 4 divisors (see below), whose sum is σ = 259572. Its totient is φ = 173040.

The previous prime is 216289. The next prime is 216317. The reversal of 216305 is 503612.

216305 is nontrivially palindromic in base 14.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 97969 + 118336 = 313^2 + 344^2 .

It is not a de Polignac number, because 216305 - 2⁴ = 216289 is a prime.

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

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21626 + ... + 21635.

It is an arithmetic number, because the mean of its divisors is an integer number (64893).

2²¹⁶³⁰⁵ is an apocalyptic number.

It is an amenable number.

216305 is a deficient number, since it is larger than the sum of its proper divisors (43267).

216305 is an equidigital number, since it uses as much as digits as its factorization.

216305 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43266.

The product of its (nonzero) digits is 180, while the sum is 17.

The square root of 216305 is about 465.0860135502. The cubic root of 216305 is about 60.0282274588.

Adding to 216305 its reverse (503612), we get a palindrome (719917).

The spelling of 216305 in words is "two hundred sixteen thousand, three hundred five".