661686 has 8 divisors (see below), whose sum is σ = 1323384. Its totient is φ = 220560.

The previous prime is 661679. The next prime is 661697. The reversal of 661686 is 686166.

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

661686 is an admirable number.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

661686 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 55135 + ... + 55146.

It is an arithmetic number, because the mean of its divisors is an integer number (165423).

2⁶⁶¹⁶⁸⁶ is an apocalyptic number.

661686 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661686 is a wasteful number, since it uses less digits than its factorization.

661686 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110286.

The product of its digits is 10368, while the sum is 33.

The square root of 661686 is about 813.4408398894. The cubic root of 661686 is about 87.1399517850.

The spelling of 661686 in words is "six hundred sixty-one thousand, six hundred eighty-six".