686891 has 2 divisors, whose sum is σ = 686892. Its totient is φ = 686890.

The previous prime is 686879. The next prime is 686893. The reversal of 686891 is 198686.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 686891 - 2¹⁴ = 670507 is a prime.

Together with 686893, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (686893) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343445 + 343446.

It is an arithmetic number, because the mean of its divisors is an integer number (343446).

2⁶⁸⁶⁸⁹¹ is an apocalyptic number.

686891 is a deficient number, since it is larger than the sum of its proper divisors (1).

686891 is an equidigital number, since it uses as much as digits as its factorization.

686891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20736, while the sum is 38.

The square root of 686891 is about 828.7888754080. The cubic root of 686891 is about 88.2326402949.

The spelling of 686891 in words is "six hundred eighty-six thousand, eight hundred ninety-one".