216660091 has 2 divisors, whose sum is σ = 216660092. Its totient is φ = 216660090.

The previous prime is 216660061. The next prime is 216660181. The reversal of 216660091 is 190066612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 216660091 - 2⁹ = 216659579 is a prime.

It is not a weakly prime, because it can be changed into another prime (216660061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108330045 + 108330046.

It is an arithmetic number, because the mean of its divisors is an integer number (108330046).

Almost surely, 2^216660091 is an apocalyptic number.

216660091 is a deficient number, since it is larger than the sum of its proper divisors (1).

216660091 is an equidigital number, since it uses as much as digits as its factorization.

216660091 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3888, while the sum is 31.

The square root of 216660091 is about 14719.3780778945. The cubic root of 216660091 is about 600.6105738256.

The spelling of 216660091 in words is "two hundred sixteen million, six hundred sixty thousand, ninety-one".