686621321 has 4 divisors (see below), whose sum is σ = 705178692. Its totient is φ = 668063952.

The previous prime is 686621317. The next prime is 686621357. The reversal of 686621321 is 123126686.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 123126686 = 2 ⋅61563343.

It can be written as a sum of positive squares in 2 ways, for example, as 510262921 + 176358400 = 22589^2 + 13280^2 .

It is a cyclic number.

It is not a de Polignac number, because 686621321 - 2² = 686621317 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (686624321) 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, 9278630 + ... + 9278703.

It is an arithmetic number, because the mean of its divisors is an integer number (176294673).

Almost surely, 2^686621321 is an apocalyptic number.

It is an amenable number.

686621321 is a deficient number, since it is larger than the sum of its proper divisors (18557371).

686621321 is a wasteful number, since it uses less digits than its factorization.

686621321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18557370.

The product of its digits is 20736, while the sum is 35.

The square root of 686621321 is about 26203.4600959492. The cubic root of 686621321 is about 882.2109183242.

The spelling of 686621321 in words is "six hundred eighty-six million, six hundred twenty-one thousand, three hundred twenty-one".