686991605 has 8 divisors (see below), whose sum is σ = 824903352. Its totient is φ = 549251008.

The previous prime is 686991601. The next prime is 686991629. The reversal of 686991605 is 506199686.

It can be written as a sum of positive squares in 4 ways, for example, as 25421764 + 661569841 = 5042^2 + 25721^2 .

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 686991605 - 2² = 686991601 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (686991601) 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, 33782 + ... + 50151.

It is an arithmetic number, because the mean of its divisors is an integer number (103112919).

Almost surely, 2^686991605 is an apocalyptic number.

It is an amenable number.

686991605 is a deficient number, since it is larger than the sum of its proper divisors (137911747).

686991605 is a wasteful number, since it uses less digits than its factorization.

686991605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85575.

The product of its (nonzero) digits is 699840, while the sum is 50.

The square root of 686991605 is about 26210.5246990593. The cubic root of 686991605 is about 882.3694772818.

The spelling of 686991605 in words is "six hundred eighty-six million, nine hundred ninety-one thousand, six hundred five".