688739641 has 2 divisors, whose sum is σ = 688739642. Its totient is φ = 688739640.

The previous prime is 688739591. The next prime is 688739657. The reversal of 688739641 is 146937886.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 422919225 + 265820416 = 20565^2 + 16304^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-688739641 is a prime.

It is not a weakly prime, because it can be changed into another prime (688730641) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 344369820 + 344369821.

It is an arithmetic number, because the mean of its divisors is an integer number (344369821).

Almost surely, 2^688739641 is an apocalyptic number.

It is an amenable number.

688739641 is a deficient number, since it is larger than the sum of its proper divisors (1).

688739641 is an equidigital number, since it uses as much as digits as its factorization.

688739641 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1741824, while the sum is 52.

The square root of 688739641 is about 26243.8495842359. The cubic root of 688739641 is about 883.1172337480.

The spelling of 688739641 in words is "six hundred eighty-eight million, seven hundred thirty-nine thousand, six hundred forty-one".