216530138663981 has 2 divisors, whose sum is σ = 216530138663982. Its totient is φ = 216530138663980.

The previous prime is 216530138663921. The next prime is 216530138664013. The reversal of 216530138663981 is 189366831035612.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 216317645323081 + 212493340900 = 14707741^2 + 460970^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-216530138663981 is a prime.

It is a super-2 number, since 2×216530138663981² (a number of 29 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (216530138663921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108265069331990 + 108265069331991.

It is an arithmetic number, because the mean of its divisors is an integer number (108265069331991).

Almost surely, 2^{216530138663981} is an apocalyptic number.

It is an amenable number.

216530138663981 is a deficient number, since it is larger than the sum of its proper divisors (1).

216530138663981 is an equidigital number, since it uses as much as digits as its factorization.

216530138663981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 33592320, while the sum is 62.

The spelling of 216530138663981 in words is "two hundred sixteen trillion, five hundred thirty billion, one hundred thirty-eight million, six hundred sixty-three thousand, nine hundred eighty-one".