688639657 has 2 divisors, whose sum is σ = 688639658. Its totient is φ = 688639656.

The previous prime is 688639639. The next prime is 688639663. The reversal of 688639657 is 756936886.

688639657 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 548074921 + 140564736 = 23411^2 + 11856^2 .

It is a cyclic number.

It is not a de Polignac number, because 688639657 - 2⁷ = 688639529 is a prime.

It is not a weakly prime, because it can be changed into another prime (688639607) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 344319828 + 344319829.

It is an arithmetic number, because the mean of its divisors is an integer number (344319829).

Almost surely, 2^688639657 is an apocalyptic number.

It is an amenable number.

688639657 is a deficient number, since it is larger than the sum of its proper divisors (1).

688639657 is an equidigital number, since it uses as much as digits as its factorization.

688639657 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 13063680, while the sum is 58.

The square root of 688639657 is about 26241.9446116327. The cubic root of 688639657 is about 883.0744977796.

The spelling of 688639657 in words is "six hundred eighty-eight million, six hundred thirty-nine thousand, six hundred fifty-seven".