688139849 has 4 divisors (see below), whose sum is σ = 696850560. Its totient is φ = 679429140.

The previous prime is 688139813. The next prime is 688139857. The reversal of 688139849 is 948931886.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-688139849 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 688139794 and 688139803.

It is not an unprimeable number, because it can be changed into a prime (688439849) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4355237 + ... + 4355394.

It is an arithmetic number, because the mean of its divisors is an integer number (174212640).

Almost surely, 2^688139849 is an apocalyptic number.

It is an amenable number.

688139849 is a deficient number, since it is larger than the sum of its proper divisors (8710711).

688139849 is an equidigital number, since it uses as much as digits as its factorization.

688139849 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8710710.

The product of its digits is 2985984, while the sum is 56.

The square root of 688139849 is about 26232.4198083212. The cubic root of 688139849 is about 882.8608037635.

The spelling of 688139849 in words is "six hundred eighty-eight million, one hundred thirty-nine thousand, eight hundred forty-nine".