686651994 has 144 divisors (see below), whose sum is σ = 1815515208. Its totient is φ = 186810624.

The previous prime is 686651983. The next prime is 686652037. The reversal of 686651994 is 499156686.

It is a happy number.

686651994 is a `hidden beast` number, since 68 + 66 + 519 + 9 + 4 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 685758969 + 893025 = 26187^2 + 945^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 686651994.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 1729404 + ... + 1729800.

Almost surely, 2^686651994 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 686651994, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (907757604).

686651994 is an abundant number, since it is smaller than the sum of its proper divisors (1128863214).

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

686651994 is a wasteful number, since it uses less digits than its factorization.

686651994 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 509 (or 499 counting only the distinct ones).

The product of its digits is 2799360, while the sum is 54.

The square root of 686651994 is about 26204.0453747127. The cubic root of 686651994 is about 882.2240549453.

The spelling of 686651994 in words is "six hundred eighty-six million, six hundred fifty-one thousand, nine hundred ninety-four".