686755991 has 4 divisors (see below), whose sum is σ = 687221184. Its totient is φ = 686290800.

The previous prime is 686755973. The next prime is 686755997. The reversal of 686755991 is 199557686.

686755991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-686755991 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 (686755997) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 230375 + ... + 233336.

It is an arithmetic number, because the mean of its divisors is an integer number (171805296).

Almost surely, 2^686755991 is an apocalyptic number.

686755991 is a deficient number, since it is larger than the sum of its proper divisors (465193).

686755991 is a wasteful number, since it uses less digits than its factorization.

686755991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 465192.

The product of its digits is 4082400, while the sum is 56.

The square root of 686755991 is about 26206.0296687613. The cubic root of 686755991 is about 882.2685918307.

The spelling of 686755991 in words is "six hundred eighty-six million, seven hundred fifty-five thousand, nine hundred ninety-one".