216539221 has 2 divisors, whose sum is σ = 216539222. Its totient is φ = 216539220.

The previous prime is 216539189. The next prime is 216539231. The reversal of 216539221 is 122935612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 179158225 + 37380996 = 13385^2 + 6114^2 .

It is a cyclic number.

It is not a de Polignac number, because 216539221 - 2⁵ = 216539189 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (216539231) 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, 108269610 + 108269611.

It is an arithmetic number, because the mean of its divisors is an integer number (108269611).

Almost surely, 2^216539221 is an apocalyptic number.

It is an amenable number.

216539221 is a deficient number, since it is larger than the sum of its proper divisors (1).

216539221 is an equidigital number, since it uses as much as digits as its factorization.

216539221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6480, while the sum is 31.

The square root of 216539221 is about 14715.2716930405. The cubic root of 216539221 is about 600.4988638136.

The spelling of 216539221 in words is "two hundred sixteen million, five hundred thirty-nine thousand, two hundred twenty-one".