685657591 has 2 divisors, whose sum is σ = 685657592. Its totient is φ = 685657590.

The previous prime is 685657571. The next prime is 685657601. The reversal of 685657591 is 195756586.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 685657591 - 2⁵ = 685657559 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (685657561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 342828795 + 342828796.

It is an arithmetic number, because the mean of its divisors is an integer number (342828796).

Almost surely, 2^685657591 is an apocalyptic number.

685657591 is a deficient number, since it is larger than the sum of its proper divisors (1).

685657591 is an equidigital number, since it uses as much as digits as its factorization.

685657591 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2268000, while the sum is 52.

The square root of 685657591 is about 26185.0642733601. The cubic root of 685657591 is about 881.7979729862.

The spelling of 685657591 in words is "six hundred eighty-five million, six hundred fifty-seven thousand, five hundred ninety-one".