688563809 has 2 divisors, whose sum is σ = 688563810. Its totient is φ = 688563808.

The previous prime is 688563797. The next prime is 688563817. The reversal of 688563809 is 908365886.

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., 545689600 + 142874209 = 23360^2 + 11953^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-688563809 is a prime.

It is not a weakly prime, because it can be changed into another prime (688563899) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 344281904 + 344281905.

It is an arithmetic number, because the mean of its divisors is an integer number (344281905).

Almost surely, 2^688563809 is an apocalyptic number.

It is an amenable number.

688563809 is a deficient number, since it is larger than the sum of its proper divisors (1).

688563809 is an equidigital number, since it uses as much as digits as its factorization.

688563809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2488320, while the sum is 53.

The square root of 688563809 is about 26240.4994045464. The cubic root of 688563809 is about 883.0420754558.

The spelling of 688563809 in words is "six hundred eighty-eight million, five hundred sixty-three thousand, eight hundred nine".