1685388778873 has 2 divisors, whose sum is σ = 1685388778874. Its totient is φ = 1685388778872.

The previous prime is 1685388778861. The next prime is 1685388778901. The reversal of 1685388778873 is 3788778835861.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1046719286649 + 638669492224 = 1023093^2 + 799168^2 .

It is a cyclic number.

It is not a de Polignac number, because 1685388778873 - 2¹⁷ = 1685388647801 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1685388778793 and 1685388778802.

It is not a weakly prime, because it can be changed into another prime (1685388778813) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 842694389436 + 842694389437.

It is an arithmetic number, because the mean of its divisors is an integer number (842694389437).

Almost surely, 2^{1685388778873} is an apocalyptic number.

It is an amenable number.

1685388778873 is a deficient number, since it is larger than the sum of its proper divisors (1).

1685388778873 is an equidigital number, since it uses as much as digits as its factorization.

1685388778873 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3034644480, while the sum is 79.

The spelling of 1685388778873 in words is "one trillion, six hundred eighty-five billion, three hundred eighty-eight million, seven hundred seventy-eight thousand, eight hundred seventy-three".