216690209 has 2 divisors, whose sum is σ = 216690210. Its totient is φ = 216690208.

The previous prime is 216690197. The next prime is 216690223. The reversal of 216690209 is 902096612.

216690209 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 127803025 + 88887184 = 11305^2 + 9428^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-216690209 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (216690709) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108345104 + 108345105.

It is an arithmetic number, because the mean of its divisors is an integer number (108345105).

Almost surely, 2^216690209 is an apocalyptic number.

It is an amenable number.

216690209 is a deficient number, since it is larger than the sum of its proper divisors (1).

216690209 is an equidigital number, since it uses as much as digits as its factorization.

216690209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 11664, while the sum is 35.

The square root of 216690209 is about 14720.4011154588. The cubic root of 216690209 is about 600.6384029027.

The spelling of 216690209 in words is "two hundred sixteen million, six hundred ninety thousand, two hundred nine".