217491091 has 2 divisors, whose sum is σ = 217491092. Its totient is φ = 217491090.

The previous prime is 217491083. The next prime is 217491103. The reversal of 217491091 is 190194712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 217491091 - 2³ = 217491083 is a prime.

It is not a weakly prime, because it can be changed into another prime (217491011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108745545 + 108745546.

It is an arithmetic number, because the mean of its divisors is an integer number (108745546).

Almost surely, 2^217491091 is an apocalyptic number.

217491091 is a deficient number, since it is larger than the sum of its proper divisors (1).

217491091 is an equidigital number, since it uses as much as digits as its factorization.

217491091 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4536, while the sum is 34.

The square root of 217491091 is about 14747.5791572719. The cubic root of 217491091 is about 601.3774749991.

The spelling of 217491091 in words is "two hundred seventeen million, four hundred ninety-one thousand, ninety-one".