216661999889 has 2 divisors, whose sum is σ = 216661999890. Its totient is φ = 216661999888.

The previous prime is 216661999867. The next prime is 216661999921. The reversal of 216661999889 is 988999166612.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 212871504400 + 3790495489 = 461380^2 + 61567^2 .

It is a cyclic number.

It is not a de Polignac number, because 216661999889 - 2²⁰ = 216660951313 is a prime.

It is not a weakly prime, because it can be changed into another prime (216661999819) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108330999944 + 108330999945.

It is an arithmetic number, because the mean of its divisors is an integer number (108330999945).

Almost surely, 2^216661999889 is an apocalyptic number.

It is an amenable number.

216661999889 is a deficient number, since it is larger than the sum of its proper divisors (1).

216661999889 is an equidigital number, since it uses as much as digits as its factorization.

216661999889 is an evil number, because the sum of its binary digits is even.

The product of its digits is 181398528, while the sum is 74.

The spelling of 216661999889 in words is "two hundred sixteen billion, six hundred sixty-one million, nine hundred ninety-nine thousand, eight hundred eighty-nine".