8491278217 has 2 divisors, whose sum is σ = 8491278218. Its totient is φ = 8491278216.

The previous prime is 8491278197. The next prime is 8491278283. The reversal of 8491278217 is 7128721948.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6320091001 + 2171187216 = 79499^2 + 46596^2 .

It is a cyclic number.

It is not a de Polignac number, because 8491278217 - 2²³ = 8482889609 is a prime.

It is not a weakly prime, because it can be changed into another prime (8491278517) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4245639108 + 4245639109.

It is an arithmetic number, because the mean of its divisors is an integer number (4245639109).

Almost surely, 2^8491278217 is an apocalyptic number.

It is an amenable number.

8491278217 is a deficient number, since it is larger than the sum of its proper divisors (1).

8491278217 is an equidigital number, since it uses as much as digits as its factorization.

8491278217 is an evil number, because the sum of its binary digits is even.

The product of its digits is 451584, while the sum is 49.

The square root of 8491278217 is about 92148.1319235501. The cubic root of 8491278217 is about 2040.1292863884.

The spelling of 8491278217 in words is "eight billion, four hundred ninety-one million, two hundred seventy-eight thousand, two hundred seventeen".