686686521 has 4 divisors (see below), whose sum is σ = 915582032. Its totient is φ = 457791012.

The previous prime is 686686519. The next prime is 686686523. The reversal of 686686521 is 125686686.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (686686519) and next prime (686686523).

It is not a de Polignac number, because 686686521 - 2¹ = 686686519 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (686686523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 114447751 + ... + 114447756.

It is an arithmetic number, because the mean of its divisors is an integer number (228895508).

Almost surely, 2^686686521 is an apocalyptic number.

It is an amenable number.

686686521 is a deficient number, since it is larger than the sum of its proper divisors (228895511).

686686521 is a wasteful number, since it uses less digits than its factorization.

686686521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 228895510.

The product of its digits is 829440, while the sum is 48.

The square root of 686686521 is about 26204.7041769221. The cubic root of 686686521 is about 882.2388416882.

The spelling of 686686521 in words is "six hundred eighty-six million, six hundred eighty-six thousand, five hundred twenty-one".