688837021 has 2 divisors, whose sum is σ = 688837022. Its totient is φ = 688837020.

The previous prime is 688837013. The next prime is 688837031. The reversal of 688837021 is 120738886.

It is a happy number.

688837021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 424936996 + 263900025 = 20614^2 + 16245^2 .

It is a cyclic number.

It is not a de Polignac number, because 688837021 - 2³ = 688837013 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (688837031) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 344418510 + 344418511.

It is an arithmetic number, because the mean of its divisors is an integer number (344418511).

Almost surely, 2^688837021 is an apocalyptic number.

It is an amenable number.

688837021 is a deficient number, since it is larger than the sum of its proper divisors (1).

688837021 is an equidigital number, since it uses as much as digits as its factorization.

688837021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 129024, while the sum is 43.

The square root of 688837021 is about 26245.7048105019. The cubic root of 688837021 is about 883.1588527180.

The spelling of 688837021 in words is "six hundred eighty-eight million, eight hundred thirty-seven thousand, twenty-one".