217238209 has 2 divisors, whose sum is σ = 217238210. Its totient is φ = 217238208.

The previous prime is 217238179. The next prime is 217238233. The reversal of 217238209 is 902832712.

217238209 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., 152596609 + 64641600 = 12353^2 + 8040^2 .

It is a cyclic number.

It is not a de Polignac number, because 217238209 - 2¹³ = 217230017 is a prime.

It is not a weakly prime, because it can be changed into another prime (217238239) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108619104 + 108619105.

It is an arithmetic number, because the mean of its divisors is an integer number (108619105).

Almost surely, 2^217238209 is an apocalyptic number.

It is an amenable number.

217238209 is a deficient number, since it is larger than the sum of its proper divisors (1).

217238209 is an equidigital number, since it uses as much as digits as its factorization.

217238209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12096, while the sum is 34.

The square root of 217238209 is about 14739.0029852769. The cubic root of 217238209 is about 601.1443060336.

The spelling of 217238209 in words is "two hundred seventeen million, two hundred thirty-eight thousand, two hundred nine".