688705657 has 4 divisors (see below), whose sum is σ = 688772196. Its totient is φ = 688639120.

The previous prime is 688705631. The next prime is 688705727. The reversal of 688705657 is 756507886.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 164249856 + 524455801 = 12816^2 + 22901^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-688705657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (688705627) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14038 + ... + 39679.

It is an arithmetic number, because the mean of its divisors is an integer number (172193049).

Almost surely, 2^688705657 is an apocalyptic number.

It is an amenable number.

688705657 is a deficient number, since it is larger than the sum of its proper divisors (66539).

688705657 is a wasteful number, since it uses less digits than its factorization.

688705657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66538.

The product of its (nonzero) digits is 2822400, while the sum is 52.

The square root of 688705657 is about 26243.2021102609. The cubic root of 688705657 is about 883.1027084964.

The spelling of 688705657 in words is "six hundred eighty-eight million, seven hundred five thousand, six hundred fifty-seven".