216138961 has 2 divisors, whose sum is σ = 216138962. Its totient is φ = 216138960.

The previous prime is 216138919. The next prime is 216138971. The reversal of 216138961 is 169831612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 137710225 + 78428736 = 11735^2 + 8856^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-216138961 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 216138961.

It is not a weakly prime, because it can be changed into another prime (216138971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108069480 + 108069481.

It is an arithmetic number, because the mean of its divisors is an integer number (108069481).

Almost surely, 2^216138961 is an apocalyptic number.

It is an amenable number.

216138961 is a deficient number, since it is larger than the sum of its proper divisors (1).

216138961 is an equidigital number, since it uses as much as digits as its factorization.

216138961 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15552, while the sum is 37.

The square root of 216138961 is about 14701.6652458148. The cubic root of 216138961 is about 600.1286400102.

The spelling of 216138961 in words is "two hundred sixteen million, one hundred thirty-eight thousand, nine hundred sixty-one".