678813391561 has 2 divisors, whose sum is σ = 678813391562. Its totient is φ = 678813391560.

The previous prime is 678813391507. The next prime is 678813391567. The reversal of 678813391561 is 165193318876.

It is a happy number.

678813391561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 632907758025 + 45905633536 = 795555^2 + 214256^2 .

It is a cyclic number.

It is not a de Polignac number, because 678813391561 - 2⁹ = 678813391049 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 678813391496 and 678813391505.

It is not a weakly prime, because it can be changed into another prime (678813391567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 339406695780 + 339406695781.

It is an arithmetic number, because the mean of its divisors is an integer number (339406695781).

Almost surely, 2^678813391561 is an apocalyptic number.

It is an amenable number.

678813391561 is a deficient number, since it is larger than the sum of its proper divisors (1).

678813391561 is an equidigital number, since it uses as much as digits as its factorization.

678813391561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6531840, while the sum is 58.

The spelling of 678813391561 in words is "six hundred seventy-eight billion, eight hundred thirteen million, three hundred ninety-one thousand, five hundred sixty-one".