686637819 has 24 divisors (see below), whose sum is σ = 1142435840. Its totient is φ = 389270448.

The previous prime is 686637779. The next prime is 686637841. The reversal of 686637819 is 918736686.

It is a happy number.

It is not a de Polignac number, because 686637819 - 2⁸ = 686637563 is a prime.

It is a super-2 number, since 2×686637819² = 942942988962153522, which contains 22 as substring.

It is a Smith number, since the sum of its digits (54) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (686637319) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 34909 + ... + 50910.

Almost surely, 2^686637819 is an apocalyptic number.

686637819 is a deficient number, since it is larger than the sum of its proper divisors (455798021).

686637819 is a wasteful number, since it uses less digits than its factorization.

686637819 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 85959 (or 85956 counting only the distinct ones).

The product of its digits is 2612736, while the sum is 54.

The square root of 686637819 is about 26203.7748998117. The cubic root of 686637819 is about 882.2179841302.

The spelling of 686637819 in words is "six hundred eighty-six million, six hundred thirty-seven thousand, eight hundred nineteen".