685586981 has 2 divisors, whose sum is σ = 685586982. Its totient is φ = 685586980.

The previous prime is 685586977. The next prime is 685586987. The reversal of 685586981 is 189685586.

685586981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 528586081 + 157000900 = 22991^2 + 12530^2 .

It is a cyclic number.

It is not a de Polignac number, because 685586981 - 2² = 685586977 is a prime.

It is a super-2 number, since 2×685586981² = 940059017033388722, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (685586987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 342793490 + 342793491.

It is an arithmetic number, because the mean of its divisors is an integer number (342793491).

Almost surely, 2^685586981 is an apocalyptic number.

It is an amenable number.

685586981 is a deficient number, since it is larger than the sum of its proper divisors (1).

685586981 is an equidigital number, since it uses as much as digits as its factorization.

685586981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4147200, while the sum is 56.

The square root of 685586981 is about 26183.7159509494. The cubic root of 685586981 is about 881.7677023413.

The spelling of 685586981 in words is "six hundred eighty-five million, five hundred eighty-six thousand, nine hundred eighty-one".