685107815721 has 8 divisors (see below), whose sum is σ = 1043973814464. Its totient is φ = 391490180400.

The previous prime is 685107815713. The next prime is 685107815737. The reversal of 685107815721 is 127518701586.

It is a happy number.

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

It is not a de Polignac number, because 685107815721 - 2³ = 685107815713 is a prime.

It is not an unprimeable number, because it can be changed into a prime (685107815701) 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, 16312090830 + ... + 16312090871.

It is an arithmetic number, because the mean of its divisors is an integer number (130496726808).

Almost surely, 2^685107815721 is an apocalyptic number.

It is an amenable number.

685107815721 is a deficient number, since it is larger than the sum of its proper divisors (358865998743).

685107815721 is a wasteful number, since it uses less digits than its factorization.

685107815721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32624181711.

The product of its (nonzero) digits is 940800, while the sum is 51.

The spelling of 685107815721 in words is "six hundred eighty-five billion, one hundred seven million, eight hundred fifteen thousand, seven hundred twenty-one".