821678860817 has 2 divisors, whose sum is σ = 821678860818. Its totient is φ = 821678860816.

The previous prime is 821678860787. The next prime is 821678860819. The reversal of 821678860817 is 718068876128.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 819533688961 + 2145171856 = 905281^2 + 46316^2 .

It is a cyclic number.

It is not a de Polignac number, because 821678860817 - 2⁶ = 821678860753 is a prime.

Together with 821678860819, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 821678860817.

It is not a weakly prime, because it can be changed into another prime (821678860819) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410839430408 + 410839430409.

It is an arithmetic number, because the mean of its divisors is an integer number (410839430409).

Almost surely, 2^821678860817 is an apocalyptic number.

It is an amenable number.

821678860817 is a deficient number, since it is larger than the sum of its proper divisors (1).

821678860817 is an equidigital number, since it uses as much as digits as its factorization.

821678860817 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 14450688, while the sum is 62.

The spelling of 821678860817 in words is "eight hundred twenty-one billion, six hundred seventy-eight million, eight hundred sixty thousand, eight hundred seventeen".