686666687 has 4 divisors (see below), whose sum is σ = 784761936. Its totient is φ = 588571440.

The previous prime is 686666671. The next prime is 686666711. The reversal of 686666687 is 786666686.

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

It is a cyclic number.

It is not a de Polignac number, because 686666687 - 2⁴ = 686666671 is a prime.

It is a super-2 number, since 2×686666687² = 943022278071111938, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (686686687) 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, 49047614 + ... + 49047627.

It is an arithmetic number, because the mean of its divisors is an integer number (196190484).

Almost surely, 2^686666687 is an apocalyptic number.

686666687 is a deficient number, since it is larger than the sum of its proper divisors (98095249).

686666687 is an equidigital number, since it uses as much as digits as its factorization.

686666687 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 98095248.

The product of its digits is 20901888, while the sum is 59.

The square root of 686666687 is about 26204.3257306881. The cubic root of 686666687 is about 882.2303475194.

Subtracting 686666687 from its reverse (786666686), we obtain a palindrome (99999999).

The spelling of 686666687 in words is "six hundred eighty-six million, six hundred sixty-six thousand, six hundred eighty-seven".