216658661 has 2 divisors, whose sum is σ = 216658662. Its totient is φ = 216658660.

The previous prime is 216658633. The next prime is 216658669. The reversal of 216658661 is 166856612.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 163456225 + 53202436 = 12785^2 + 7294^2 .

It is a cyclic number.

It is not a de Polignac number, because 216658661 - 2¹⁸ = 216396517 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (216658669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108329330 + 108329331.

It is an arithmetic number, because the mean of its divisors is an integer number (108329331).

Almost surely, 2^216658661 is an apocalyptic number.

It is an amenable number.

216658661 is a deficient number, since it is larger than the sum of its proper divisors (1).

216658661 is an equidigital number, since it uses as much as digits as its factorization.

216658661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 103680, while the sum is 41.

The square root of 216658661 is about 14719.3295023924. The cubic root of 216658661 is about 600.6092524393.

The spelling of 216658661 in words is "two hundred sixteen million, six hundred fifty-eight thousand, six hundred sixty-one".