216305661 has 16 divisors (see below), whose sum is σ = 338829120. Its totient is φ = 121009920.

The previous prime is 216305659. The next prime is 216305669. The reversal of 216305661 is 166503612.

It is not a de Polignac number, because 216305661 - 2¹ = 216305659 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216305669) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 251676 + ... + 252533.

It is an arithmetic number, because the mean of its divisors is an integer number (21176820).

Almost surely, 2^216305661 is an apocalyptic number.

It is an amenable number.

216305661 is a deficient number, since it is larger than the sum of its proper divisors (122523459).

216305661 is a wasteful number, since it uses less digits than its factorization.

216305661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 504236.

The product of its (nonzero) digits is 6480, while the sum is 30.

The square root of 216305661 is about 14707.3335788647. Note that the first 3 decimals coincide. The cubic root of 216305661 is about 600.2828860493.

The spelling of 216305661 in words is "two hundred sixteen million, three hundred five thousand, six hundred sixty-one".