218666360021 has 2 divisors, whose sum is σ = 218666360022. Its totient is φ = 218666360020.

The previous prime is 218666360009. The next prime is 218666360063. The reversal of 218666360021 is 120063666812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 181719753796 + 36946606225 = 426286^2 + 192215^2 .

It is a cyclic number.

It is not a de Polignac number, because 218666360021 - 2¹⁰ = 218666358997 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (218666360221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109333180010 + 109333180011.

It is an arithmetic number, because the mean of its divisors is an integer number (109333180011).

Almost surely, 2^218666360021 is an apocalyptic number.

It is an amenable number.

218666360021 is a deficient number, since it is larger than the sum of its proper divisors (1).

218666360021 is an equidigital number, since it uses as much as digits as its factorization.

218666360021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 124416, while the sum is 41.

The spelling of 218666360021 in words is "two hundred eighteen billion, six hundred sixty-six million, three hundred sixty thousand, twenty-one".