217988321 has 2 divisors, whose sum is σ = 217988322. Its totient is φ = 217988320.

The previous prime is 217988299. The next prime is 217988357. The reversal of 217988321 is 123889712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 211557025 + 6431296 = 14545^2 + 2536^2 .

It is a cyclic number.

It is not a de Polignac number, because 217988321 - 2¹⁸ = 217726177 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (217988821) 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, 108994160 + 108994161.

It is an arithmetic number, because the mean of its divisors is an integer number (108994161).

Almost surely, 2^217988321 is an apocalyptic number.

It is an amenable number.

217988321 is a deficient number, since it is larger than the sum of its proper divisors (1).

217988321 is an equidigital number, since it uses as much as digits as its factorization.

217988321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 48384, while the sum is 41.

The square root of 217988321 is about 14764.4275540909. The cubic root of 217988321 is about 601.8354176414.

The spelling of 217988321 in words is "two hundred seventeen million, nine hundred eighty-eight thousand, three hundred twenty-one".