686491 has 4 divisors (see below), whose sum is σ = 739312. Its totient is φ = 633672.

The previous prime is 686479. The next prime is 686503. The reversal of 686491 is 194686.

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

It is an interprime number because it is at equal distance from previous prime (686479) and next prime (686503).

It is not a de Polignac number, because 686491 - 2⁷ = 686363 is a prime.

It is a Duffinian number.

686491 is a lucky number.

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (686891) 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, 26391 + ... + 26416.

It is an arithmetic number, because the mean of its divisors is an integer number (184828).

2⁶⁸⁶⁴⁹¹ is an apocalyptic number.

686491 is a deficient number, since it is larger than the sum of its proper divisors (52821).

686491 is a wasteful number, since it uses less digits than its factorization.

686491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52820.

The product of its digits is 10368, while the sum is 34.

The square root of 686491 is about 828.5475242857. The cubic root of 686491 is about 88.2155100131.

The spelling of 686491 in words is "six hundred eighty-six thousand, four hundred ninety-one".