688423991 has 2 divisors, whose sum is σ = 688423992. Its totient is φ = 688423990.

The previous prime is 688423987. The next prime is 688423999. The reversal of 688423991 is 199324886.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 688423991 - 2² = 688423987 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (688423999) 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, 344211995 + 344211996.

It is an arithmetic number, because the mean of its divisors is an integer number (344211996).

Almost surely, 2^688423991 is an apocalyptic number.

688423991 is a deficient number, since it is larger than the sum of its proper divisors (1).

688423991 is an equidigital number, since it uses as much as digits as its factorization.

688423991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 746496, while the sum is 50.

The square root of 688423991 is about 26237.8351050539. The cubic root of 688423991 is about 882.9823019906.

The spelling of 688423991 in words is "six hundred eighty-eight million, four hundred twenty-three thousand, nine hundred ninety-one".