217680857 has 2 divisors, whose sum is σ = 217680858. Its totient is φ = 217680856.

The previous prime is 217680821. The next prime is 217680871. The reversal of 217680857 is 758086712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 140873161 + 76807696 = 11869^2 + 8764^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-217680857 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (217680887) 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, 108840428 + 108840429.

It is an arithmetic number, because the mean of its divisors is an integer number (108840429).

Almost surely, 2^217680857 is an apocalyptic number.

It is an amenable number.

217680857 is a deficient number, since it is larger than the sum of its proper divisors (1).

217680857 is an equidigital number, since it uses as much as digits as its factorization.

217680857 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 188160, while the sum is 44.

The square root of 217680857 is about 14754.0115561836. The cubic root of 217680857 is about 601.5523293995.

The spelling of 217680857 in words is "two hundred seventeen million, six hundred eighty thousand, eight hundred fifty-seven".