686251021 has 2 divisors, whose sum is σ = 686251022. Its totient is φ = 686251020.

The previous prime is 686251009. The next prime is 686251043. The reversal of 686251021 is 120152686.

686251021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 633528900 + 52722121 = 25170^2 + 7261^2 .

It is a cyclic number.

It is not a de Polignac number, because 686251021 - 2²³ = 677862413 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (686254021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343125510 + 343125511.

It is an arithmetic number, because the mean of its divisors is an integer number (343125511).

Almost surely, 2^686251021 is an apocalyptic number.

It is an amenable number.

686251021 is a deficient number, since it is larger than the sum of its proper divisors (1).

686251021 is an equidigital number, since it uses as much as digits as its factorization.

686251021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5760, while the sum is 31.

The square root of 686251021 is about 26196.3932822822. The cubic root of 686251021 is about 882.0522954957.

The spelling of 686251021 in words is "six hundred eighty-six million, two hundred fifty-one thousand, twenty-one".