686129221 has 8 divisors (see below), whose sum is σ = 707191704. Its totient is φ = 665199360.

The previous prime is 686129207. The next prime is 686129239. The reversal of 686129221 is 122921686.

It can be written as a sum of positive squares in 4 ways, for example, as 379704196 + 306425025 = 19486^2 + 17505^2 .

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 686129221 - 2²⁹ = 149258309 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (37).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (686129251) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 22600 + ... + 43393.

It is an arithmetic number, because the mean of its divisors is an integer number (88398963).

It is a Poulet number, since it divides 2^686129220-1.

Almost surely, 2^686129221 is an apocalyptic number.

It is an amenable number.

686129221 is a deficient number, since it is larger than the sum of its proper divisors (21062483).

686129221 is a wasteful number, since it uses less digits than its factorization.

686129221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66311.

The product of its digits is 20736, while the sum is 37.

The square root of 686129221 is about 26194.0684316125. The cubic root of 686129221 is about 882.0001084082. Note that the first 3 decimals are identical.

The spelling of 686129221 in words is "six hundred eighty-six million, one hundred twenty-nine thousand, two hundred twenty-one".