685909639 has 2 divisors, whose sum is σ = 685909640. Its totient is φ = 685909638.

The previous prime is 685909579. The next prime is 685909643. The reversal of 685909639 is 936909586.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 685909639 - 2⁹ = 685909127 is a prime.

It is a super-2 number, since 2×685909639² = 940944065746220642, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 685909639.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (685909649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 342954819 + 342954820.

It is an arithmetic number, because the mean of its divisors is an integer number (342954820).

Almost surely, 2^685909639 is an apocalyptic number.

685909639 is a deficient number, since it is larger than the sum of its proper divisors (1).

685909639 is an equidigital number, since it uses as much as digits as its factorization.

685909639 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3149280, while the sum is 55.

The square root of 685909639 is about 26189.8766511032. The cubic root of 685909639 is about 881.9060095097.

The spelling of 685909639 in words is "six hundred eighty-five million, nine hundred nine thousand, six hundred thirty-nine".