686979661 has 4 divisors (see below), whose sum is σ = 688123324. Its totient is φ = 685836000.

The previous prime is 686979613. The next prime is 686979701. The reversal of 686979661 is 166979686.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 629508100 + 57471561 = 25090^2 + 7581^2 .

It is a cyclic number.

It is not a de Polignac number, because 686979661 - 2¹³ = 686971469 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 686979596 and 686979605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (686919661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 570930 + ... + 572131.

It is an arithmetic number, because the mean of its divisors is an integer number (172030831).

Almost surely, 2^686979661 is an apocalyptic number.

It is an amenable number.

686979661 is a deficient number, since it is larger than the sum of its proper divisors (1143663).

686979661 is a wasteful number, since it uses less digits than its factorization.

686979661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1143662.

The product of its digits is 5878656, while the sum is 58.

The square root of 686979661 is about 26210.2968506654. The cubic root of 686979661 is about 882.3643636424.

The spelling of 686979661 in words is "six hundred eighty-six million, nine hundred seventy-nine thousand, six hundred sixty-one".