217116661 has 2 divisors, whose sum is σ = 217116662. Its totient is φ = 217116660.

The previous prime is 217116643. The next prime is 217116719. The reversal of 217116661 is 166611712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 208080625 + 9036036 = 14425^2 + 3006^2 .

It is a cyclic number.

It is not a de Polignac number, because 217116661 - 2⁹ = 217116149 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (217116611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108558330 + 108558331.

It is an arithmetic number, because the mean of its divisors is an integer number (108558331).

Almost surely, 2^217116661 is an apocalyptic number.

It is an amenable number.

217116661 is a deficient number, since it is larger than the sum of its proper divisors (1).

217116661 is an equidigital number, since it uses as much as digits as its factorization.

217116661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3024, while the sum is 31.

The square root of 217116661 is about 14734.8790629581. The cubic root of 217116661 is about 601.0321687317.

The spelling of 217116661 in words is "two hundred seventeen million, one hundred sixteen thousand, six hundred sixty-one".