686521 has 8 divisors (see below), whose sum is σ = 756000. Its totient is φ = 618240.

The previous prime is 686519. The next prime is 686551. The reversal of 686521 is 125686.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 686521 - 2¹ = 686519 is a prime.

It is a super-2 number, since 2×686521² = 942622166882, which contains 22 as substring.

It is an Ulam number.

It is a Duffinian number.

It is a nialpdrome in base 15.

It is a self number, because there is not a number n which added to its sum of digits gives 686521.

It is not an unprimeable number, because it can be changed into a prime (686551) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1305 + ... + 1753.

It is an arithmetic number, because the mean of its divisors is an integer number (94500).

2⁶⁸⁶⁵²¹ is an apocalyptic number.

It is an amenable number.

686521 is a deficient number, since it is larger than the sum of its proper divisors (69479).

686521 is a wasteful number, since it uses less digits than its factorization.

686521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 599.

The product of its digits is 2880, while the sum is 28.

The square root of 686521 is about 828.5656280585. The cubic root of 686521 is about 88.2167950151.

It can be divided in two parts, 6865 and 21, that added together give a palindrome (6886).

The spelling of 686521 in words is "six hundred eighty-six thousand, five hundred twenty-one".