688889081 has 2 divisors, whose sum is σ = 688889082. Its totient is φ = 688889080.

The previous prime is 688889063. The next prime is 688889083. The reversal of 688889081 is 180988886.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 442681600 + 246207481 = 21040^2 + 15691^2 .

It is a cyclic number.

It is not a de Polignac number, because 688889081 - 2²⁶ = 621780217 is a prime.

It is a super-2 number, since 2×688889081² = 949136331842049122, which contains 22 as substring.

Together with 688889083, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (688889083) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 344444540 + 344444541.

It is an arithmetic number, because the mean of its divisors is an integer number (344444541).

Almost surely, 2^688889081 is an apocalyptic number.

It is an amenable number.

688889081 is a deficient number, since it is larger than the sum of its proper divisors (1).

688889081 is an equidigital number, since it uses as much as digits as its factorization.

688889081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1769472, while the sum is 56.

The square root of 688889081 is about 26246.6965730928. The cubic root of 688889081 is about 883.1811008891.

The spelling of 688889081 in words is "six hundred eighty-eight million, eight hundred eighty-nine thousand, eighty-one".