216465566921 has 2 divisors, whose sum is σ = 216465566922. Its totient is φ = 216465566920.

The previous prime is 216465566857. The next prime is 216465566959. The reversal of 216465566921 is 129665564612.

It is a happy number.

216465566921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 145285994896 + 71179572025 = 381164^2 + 266795^2 .

It is a cyclic number.

It is not a de Polignac number, because 216465566921 - 2⁶ = 216465566857 is a prime.

It is not a weakly prime, because it can be changed into another prime (216465566021) 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, 108232783460 + 108232783461.

It is an arithmetic number, because the mean of its divisors is an integer number (108232783461).

Almost surely, 2^216465566921 is an apocalyptic number.

It is an amenable number.

216465566921 is a deficient number, since it is larger than the sum of its proper divisors (1).

216465566921 is an equidigital number, since it uses as much as digits as its factorization.

216465566921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4665600, while the sum is 53.

The spelling of 216465566921 in words is "two hundred sixteen billion, four hundred sixty-five million, five hundred sixty-six thousand, nine hundred twenty-one".