13216561 has 2 divisors, whose sum is σ = 13216562. Its totient is φ = 13216560.

The previous prime is 13216549. The next prime is 13216583. The reversal of 13216561 is 16561231.

13216561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13184161 + 32400 = 3631^2 + 180^2 .

It is a cyclic number.

It is not a de Polignac number, because 13216561 - 2⁷ = 13216433 is a prime.

It is not a weakly prime, because it can be changed into another prime (13216661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6608280 + 6608281.

It is an arithmetic number, because the mean of its divisors is an integer number (6608281).

Almost surely, 2^13216561 is an apocalyptic number.

It is an amenable number.

13216561 is a deficient number, since it is larger than the sum of its proper divisors (1).

13216561 is an equidigital number, since it uses as much as digits as its factorization.

13216561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1080, while the sum is 25.

The square root of 13216561 is about 3635.4588431173. The cubic root of 13216561 is about 236.4319449827.

Adding to 13216561 its reverse (16561231), we get a palindrome (29777792).

The spelling of 13216561 in words is "thirteen million, two hundred sixteen thousand, five hundred sixty-one".