688739657 has 2 divisors, whose sum is σ = 688739658. Its totient is φ = 688739656.

The previous prime is 688739641. The next prime is 688739663. The reversal of 688739657 is 756937886.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 565440841 + 123298816 = 23779^2 + 11104^2 .

It is a cyclic number.

It is not a de Polignac number, because 688739657 - 2⁴ = 688739641 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 688739596 and 688739605.

It is not a weakly prime, because it can be changed into another prime (688739677) 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 as a sum of consecutive naturals, namely, 344369828 + 344369829.

It is an arithmetic number, because the mean of its divisors is an integer number (344369829).

Almost surely, 2^688739657 is an apocalyptic number.

It is an amenable number.

688739657 is a deficient number, since it is larger than the sum of its proper divisors (1).

688739657 is an equidigital number, since it uses as much as digits as its factorization.

688739657 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15240960, while the sum is 59.

The square root of 688739657 is about 26243.8498890692. The cubic root of 688739657 is about 883.1172405865.

The spelling of 688739657 in words is "six hundred eighty-eight million, seven hundred thirty-nine thousand, six hundred fifty-seven".