688105021 has 8 divisors (see below), whose sum is σ = 713703384. Its totient is φ = 662875200.

The previous prime is 688105003. The next prime is 688105027. The reversal of 688105021 is 120501886.

It can be written as a sum of positive squares in 4 ways, for example, as 534072100 + 154032921 = 23110^2 + 12411^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 688105021 - 2¹¹ = 688102973 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (688105027) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 88330 + ... + 95803.

It is an arithmetic number, because the mean of its divisors is an integer number (89212923).

Almost surely, 2^688105021 is an apocalyptic number.

It is an amenable number.

688105021 is a deficient number, since it is larger than the sum of its proper divisors (25598363).

688105021 is a wasteful number, since it uses less digits than its factorization.

688105021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 184271.

The product of its (nonzero) digits is 3840, while the sum is 31.

The square root of 688105021 is about 26231.7559648606. The cubic root of 688105021 is about 882.8459091192.

The spelling of 688105021 in words is "six hundred eighty-eight million, one hundred five thousand, twenty-one".