216538891 has 2 divisors, whose sum is σ = 216538892. Its totient is φ = 216538890.

The previous prime is 216538873. The next prime is 216538901. The reversal of 216538891 is 198835612.

216538891 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 216538891 - 2¹⁵ = 216506123 is a prime.

It is not a weakly prime, because it can be changed into another prime (216538811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108269445 + 108269446.

It is an arithmetic number, because the mean of its divisors is an integer number (108269446).

Almost surely, 2^216538891 is an apocalyptic number.

216538891 is a deficient number, since it is larger than the sum of its proper divisors (1).

216538891 is an equidigital number, since it uses as much as digits as its factorization.

216538891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 103680, while the sum is 43.

The square root of 216538891 is about 14715.2604801954. The cubic root of 216538891 is about 600.4985587653.

The spelling of 216538891 in words is "two hundred sixteen million, five hundred thirty-eight thousand, eight hundred ninety-one".