685984609 has 2 divisors, whose sum is σ = 685984610. Its totient is φ = 685984608.

The previous prime is 685984603. The next prime is 685984613. The reversal of 685984609 is 906489586.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 612711009 + 73273600 = 24753^2 + 8560^2 .

It is a cyclic number.

It is not a de Polignac number, because 685984609 - 2³ = 685984601 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 685984609.

It is not a weakly prime, because it can be changed into another prime (685984601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 342992304 + 342992305.

It is an arithmetic number, because the mean of its divisors is an integer number (342992305).

Almost surely, 2^685984609 is an apocalyptic number.

It is an amenable number.

685984609 is a deficient number, since it is larger than the sum of its proper divisors (1).

685984609 is an equidigital number, since it uses as much as digits as its factorization.

685984609 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3732480, while the sum is 55.

The square root of 685984609 is about 26191.3078902143. The cubic root of 685984609 is about 881.9381391475.

The spelling of 685984609 in words is "six hundred eighty-five million, nine hundred eighty-four thousand, six hundred nine".