217018819711721 has 2 divisors, whose sum is σ = 217018819711722. Its totient is φ = 217018819711720.

The previous prime is 217018819711709. The next prime is 217018819711739. The reversal of 217018819711721 is 127117918810712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 165019433388121 + 51999386323600 = 12845989^2 + 7211060^2 .

It is a cyclic number.

It is not a de Polignac number, because 217018819711721 - 2⁴⁶ = 146650075534057 is a prime.

It is not a weakly prime, because it can be changed into another prime (217018819714721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108509409855860 + 108509409855861.

It is an arithmetic number, because the mean of its divisors is an integer number (108509409855861).

Almost surely, 2^{217018819711721} is an apocalyptic number.

It is an amenable number.

217018819711721 is a deficient number, since it is larger than the sum of its proper divisors (1).

217018819711721 is an equidigital number, since it uses as much as digits as its factorization.

217018819711721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 790272, while the sum is 56.

The spelling of 217018819711721 in words is "two hundred seventeen trillion, eighteen billion, eight hundred nineteen million, seven hundred eleven thousand, seven hundred twenty-one".