216561420161 has 2 divisors, whose sum is σ = 216561420162. Its totient is φ = 216561420160.

The previous prime is 216561420149. The next prime is 216561420193. The reversal of 216561420161 is 161024165612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 211824539536 + 4736880625 = 460244^2 + 68825^2 .

It is a cyclic number.

It is not a de Polignac number, because 216561420161 - 2³⁰ = 215487678337 is a prime.

It is not a weakly prime, because it can be changed into another prime (216561420961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108280710080 + 108280710081.

It is an arithmetic number, because the mean of its divisors is an integer number (108280710081).

Almost surely, 2^216561420161 is an apocalyptic number.

It is an amenable number.

216561420161 is a deficient number, since it is larger than the sum of its proper divisors (1).

216561420161 is an equidigital number, since it uses as much as digits as its factorization.

216561420161 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 17280, while the sum is 35.

Adding to 216561420161 its reverse (161024165612), we get a palindrome (377585585773).

The spelling of 216561420161 in words is "two hundred sixteen billion, five hundred sixty-one million, four hundred twenty thousand, one hundred sixty-one".