216306661 has 4 divisors (see below), whose sum is σ = 219044800. Its totient is φ = 213568524.

The previous prime is 216306653. The next prime is 216306667. The reversal of 216306661 is 166603612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 216306661 - 2³ = 216306653 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216306667) 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, 1368951 + ... + 1369108.

It is an arithmetic number, because the mean of its divisors is an integer number (54761200).

Almost surely, 2^216306661 is an apocalyptic number.

It is an amenable number.

216306661 is a deficient number, since it is larger than the sum of its proper divisors (2738139).

216306661 is an equidigital number, since it uses as much as digits as its factorization.

216306661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2738138.

The product of its (nonzero) digits is 7776, while the sum is 31.

The square root of 216306661 is about 14707.3675754705. The cubic root of 216306661 is about 600.2838111013.

The spelling of 216306661 in words is "two hundred sixteen million, three hundred six thousand, six hundred sixty-one".