815905217 has 2 divisors, whose sum is σ = 815905218. Its totient is φ = 815905216.

The previous prime is 815905193. The next prime is 815905219. The reversal of 815905217 is 712509518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 496353841 + 319551376 = 22279^2 + 17876^2 .

It is a cyclic number.

It is not a de Polignac number, because 815905217 - 2¹⁴ = 815888833 is a prime.

Together with 815905219, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (815905219) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 407952608 + 407952609.

It is an arithmetic number, because the mean of its divisors is an integer number (407952609).

Almost surely, 2^815905217 is an apocalyptic number.

It is an amenable number.

815905217 is a deficient number, since it is larger than the sum of its proper divisors (1).

815905217 is an equidigital number, since it uses as much as digits as its factorization.

815905217 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 25200, while the sum is 38.

The square root of 815905217 is about 28564.0546316520. The cubic root of 815905217 is about 934.4295631154.

The spelling of 815905217 in words is "eight hundred fifteen million, nine hundred five thousand, two hundred seventeen".