685312991 has 16 divisors (see below), whose sum is σ = 799158528. Its totient is φ = 581380800.

The previous prime is 685312987. The next prime is 685313003. The reversal of 685312991 is 199213586.

It is a happy number.

It is not a de Polignac number, because 685312991 - 2² = 685312987 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (685312981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22661 + ... + 43406.

It is an arithmetic number, because the mean of its divisors is an integer number (49947408).

Almost surely, 2^685312991 is an apocalyptic number.

685312991 is a deficient number, since it is larger than the sum of its proper divisors (113845537).

685312991 is a wasteful number, since it uses less digits than its factorization.

685312991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66142.

The product of its digits is 116640, while the sum is 44.

The square root of 685312991 is about 26178.4833594309. The cubic root of 685312991 is about 881.6502226096.

The spelling of 685312991 in words is "six hundred eighty-five million, three hundred twelve thousand, nine hundred ninety-one".