688509961 has 2 divisors, whose sum is σ = 688509962. Its totient is φ = 688509960.

The previous prime is 688509947. The next prime is 688510021. The reversal of 688509961 is 169905886.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 499969600 + 188540361 = 22360^2 + 13731^2 .

It is a cyclic number.

It is not a de Polignac number, because 688509961 - 2⁹ = 688509449 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 688509899 and 688509908.

It is not a weakly prime, because it can be changed into another prime (688509901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 344254980 + 344254981.

It is an arithmetic number, because the mean of its divisors is an integer number (344254981).

Almost surely, 2^688509961 is an apocalyptic number.

It is an amenable number.

688509961 is a deficient number, since it is larger than the sum of its proper divisors (1).

688509961 is an equidigital number, since it uses as much as digits as its factorization.

688509961 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 933120, while the sum is 52.

The square root of 688509961 is about 26239.4733369403. The cubic root of 688509961 is about 883.0190559048.

The spelling of 688509961 in words is "six hundred eighty-eight million, five hundred nine thousand, nine hundred sixty-one".