217097891 has 2 divisors, whose sum is σ = 217097892. Its totient is φ = 217097890.

The previous prime is 217097887. The next prime is 217097921. The reversal of 217097891 is 198790712.

217097891 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 is a cyclic number.

It is not a de Polignac number, because 217097891 - 2² = 217097887 is a prime.

It is not a weakly prime, because it can be changed into another prime (217097831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108548945 + 108548946.

It is an arithmetic number, because the mean of its divisors is an integer number (108548946).

Almost surely, 2^217097891 is an apocalyptic number.

217097891 is a deficient number, since it is larger than the sum of its proper divisors (1).

217097891 is an equidigital number, since it uses as much as digits as its factorization.

217097891 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 63504, while the sum is 44.

The square root of 217097891 is about 14734.2421250636. The cubic root of 217097891 is about 601.0148482447.

The spelling of 217097891 in words is "two hundred seventeen million, ninety-seven thousand, eight hundred ninety-one".