216664909 has 2 divisors, whose sum is σ = 216664910. Its totient is φ = 216664908.

The previous prime is 216664879. The next prime is 216664913. The reversal of 216664909 is 909466612.

It is a happy number.

216664909 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 121660900 + 95004009 = 11030^2 + 9747^2 .

It is a cyclic number.

It is not a de Polignac number, because 216664909 - 2⁷ = 216664781 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (216664919) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108332454 + 108332455.

It is an arithmetic number, because the mean of its divisors is an integer number (108332455).

Almost surely, 2^216664909 is an apocalyptic number.

It is an amenable number.

216664909 is a deficient number, since it is larger than the sum of its proper divisors (1).

216664909 is an equidigital number, since it uses as much as digits as its factorization.

216664909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 139968, while the sum is 43.

The square root of 216664909 is about 14719.5417387906. The cubic root of 216664909 is about 600.6150258381.

The spelling of 216664909 in words is "two hundred sixteen million, six hundred sixty-four thousand, nine hundred nine".